Investors / United States / Castle Island Ventures
Castle Island Ventures
Venture capital · Boston, MA, United States · North America
Castle Island Ventures is a venture capital firm focused exclusively on public blockchains. It supports entrepreneurs building the infrastructure and application companies needed for these protocols to reach their potential.
Invests inFintech
In its own wordsblockchaincryptofintechinfrastructuredigital assets
Your fit with Castle Island Ventures
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See how your round matches what it backs, point by point.
Or find every investor that fitsCastle Island Ventures lists 25 checked portfolio companies on its own site and is named in 15 funding rounds, 7 of them as lead. Its most frequent entry is Seed, 50% of the companies with a known first round. Its largest themes are Fintech (58%), Cybersecurity (11%) and Crypto & Web3 (11%). 91% of its companies are based in United States. It invests most often alongside Andreessen Horowitz, a16z Frontier and Blockchain Capital.
Counts come from funding rounds that name Castle Island Ventures, complete from mid-2025: earlier rounds appear only when they were reported later. Round amounts and full round histories are on Fundup AI.
Round figures show recent activity, not Castle Island Ventures' whole history. Rounds on record name 12 companies; its own site lists 25. Funding rounds are complete from mid-2025, so counts and the yearly trend undercount a firm that invested before then. The portfolio, themes and places come from its own site and are not affected.
Entry stage
share of companies by the stage of its first roundShow as a table
| Value | |
|---|---|
| Pre-seed | 0% |
| Seed | 50% |
| Series A | 42% |
| Series B | 8% |
| Growth | 0% |
Activity by year
rounds it joined, last 10 yearsShow as a table
| Total | Rounds it led | |
|---|---|---|
| '17 | 0 | 0 |
| '18 | 0 | 0 |
| '19 | 0 | 0 |
| '20 | 0 | 0 |
| '21 | 1 | 0 |
| '22 | 0 | 0 |
| '23 | 1 | 0 |
| '24 | 0 | 0 |
| '25 | 3 | 2 |
| '26 | 10 | 5 |
Investor profile
percentile among all firmsShow as a table
| Measure | Percentile of all firms | Value |
|---|---|---|
| Portfolio size | 60th | 25 companies |
| Recent activity | 95th | 10 rounds in 12 months |
| Early stage | 73th | 50% of entries at pre-seed or seed |
| Evidence | 87th | 16% of companies confirmed by a round |
| Sector focus | 88th | 58% in its largest sector |
| Reach | 58th | 3 countries |
Investment themes
share of its checked companiesThis firmAll checked companies
Show as a table
| This firm | All checked companies | |
|---|---|---|
| Fintech | 58% | 12% |
| Cybersecurity | 11% | 4% |
| Crypto & Web3 | 11% | 1% |
| Real Estate & Construction | 5% | 3% |
| Legal & Compliance | 5% | 2% |
| AI & Machine Learning | 3% | 18% |
| Enterprise Software | 3% | 8% |
| Consumer | 3% | 3% |
Invests most often with
firms sharing its portfolio companiesShow as a table
| Share | |
|---|---|
| Andreessen Horowitz | 5 |
| a16z Frontier | 4 |
| Blockchain Capital | 3 |
| Founders Fund | 3 |
| ParaFi Capital | 3 |
| Pharsalus Capital | 3 |
| Y Combinator | 3 |
| Chapter One | 2 |
Its portfolio companies
where they are based, and what their own sites showSite status
- Site answers25100%
- No longer answers00%
- Points to another company00%
- Parked or sold domain00%
A site that stops answering three checks in a row is counted as no longer answering; that is not proof of closure. A site that points to another company is often an acquisition.
Co-investor network
who it backs companies with, and who they back togetherAll co-investors or Compare portfolios with Andreessen Horowitz
Compare Castle Island Ventures head to head
portfolio size, rounds, entry stages, themes and the companies both backThree or more firms at once: portfolio overlap.
Recent portfolio activity
when companies last raised with Castle Island Ventures| Date | Company | Stage |
|---|---|---|
| 28 Oct 2026 | Seed | |
| 1 Sept 2026 | Series C+ | |
| 1 Sept 2026 | Series B | |
| 28 Jul 2026 | Seed Led | |
| 15 Jul 2026 | Series A | |
| 30 Mar 2026 | Seed Led | |
| 26 Mar 2026 | Series A Led | |
| 4 Mar 2026 | Series A Led |
Round details for Castle Island Ventures
Amounts, full round histories and every co-investor in Castle Island Ventures' rounds are on Fundup AI. VCinfo covers investors and their portfolios.
Portfolio
25 companies checked against their own sites| Company | What it does | Themes | First round with it | Evidence |
|---|---|---|---|---|
| Alpen Labs provides financial products and services on the Bitcoin market using zero-knowledge proofs for security. | FintechCrypto & Web3 | Portfolio page | ||
| Andrena provides high-speed internet services to residents, buildings, and businesses. | Enterprise SoftwareConsumer | Portfolio page | ||
| Arch offers loans backed by cryptocurrencies such as Bitcoin, Ethereum, Solana, and XRP | Fintech | Portfolio page | ||
| ARQ provides financial services, including currency conversion, investment, and payment services, to individuals and businesses globally. | FintechFintech | Portfolio page | ||
| Arx Research provides Medical Affairs benchmarking solutions to pharmaceutical executives | Healthcare & Biotech | Nov 2025Seed | Funding round | |
| Atrium unifies bank balance sheets, securitized loans, insurance portfolios, and county records into one loan-level intelligence layer for real estate capital markets. | FintechReal Estate & Construction | Portfolio page | ||
| Attestiv validates digital files such as photos, documents, audio, and video using AI analysis to prevent fraud and errors | CybersecurityFintech | Portfolio page | ||
| Babylon unlocks capital efficiency for native Bitcoin, trustlessly and in a self-custodial infrastructure. | Fintech | Portfolio page | ||
| Birch Hill provides credit products and asset management services, including onchain credit and private credit offerings for institutions. | FintechLegal & Compliance | Feb 2026Seed · 2 rounds | Funding round | |
| Birdai measures and aims to return the value lost between an order and its fill in on-chain markets | Fintech | Jul 2026Seed | Funding round | |
| Bitwise provides professionally managed exposure to crypto opportunities through various financial products, including ETFs and index funds. | Fintech | Portfolio page | ||
| Cyclops provides crypto and stablecoin solutions for payments companies | FintechCrypto & Web3 | Mar 2026Series A · 2 rounds | Funding round | |
| Fireblocks Dynamic provides embedded wallets and onchain finance solutions for digital assets | FintechCrypto & Web3 | Dec 2023Series A | Funding round | |
| Portfolio page | ||||
| The company allows users to send money to Latin America via WhatsApp | Fintech | Sept 2026Series B · 2 rounds | Page + round | |
| Groma owns and manages properties, offering rentals and investment opportunities | Real Estate & Construction | Portfolio page | ||
| OpenFX provides instant cross-border payment infrastructure and foreign exchange liquidity | FintechFintech | May 2025Seed | Funding round | |
| Project Eleven provides digital asset custody and blockchain infrastructure security solutions | FintechCybersecurity | Jan 2026Series A | Page + round | |
| Station70 builds security products for what enterprises can least afford to lose: keys, identities, and access. | CybersecurityAI & Machine Learning | Portfolio page | ||
| Talos provides a platform for trading, managing, and accessing digital assets at an institutional scale. | FintechCrypto & Web3 | May 2021Series A | Page + round |
About this data
site last read 5 Nov 2026- Site
- castleisland.vc
- Last read
- 5 Nov 2026
- Watching since
- 5 Nov 2026
- Rounds since
- 27 May 2021
- Companies checked
- 25
Rates come from what VCinfo has observed since observation_start. Firms tend to remove companies that closed, so early rates understate reality. A company leaving a portfolio page does not mean it closed or exited. An unreachable site means our checks failed, nothing more.
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