As of November 6, 2026, 3 holders' latest Schedule 13D or 13G filings report owning 5% or more of Westamerica BanCorp. The largest reported stake is American Century Investment Management, Inc.'s, at 8.3%. 6 filings are on record since March 27, 2026 (Schedule 13G/A, August 14, 2026).
Sell to companies like Westamerica BanCorp? Enter your website and see 10 with a filed reason to buy from you this month. Free.
Opens in a new tab. No signup.
Key facts
- · Reporting person: Vanguard Capital Management · Sole voting: 169,595 · Shared voting: 0 · Sole dispositive: 1,134,029 · Shared dispositive: 0 · SCHEDULE 13G/A, 2026-10-30
- · Reporting person: American Century Investment Management, Inc. · Sole voting: 1,920,874 · Shared voting: 0 · Sole dispositive: 1,958,072 · Shared dispositive: 0 · SCHEDULE 13G/A, 2026-08-14
- · Reporting person: State Street Corporation · Sole voting: 0 · Shared voting: 283,756 · Sole dispositive: 0 · Shared dispositive: 1,394,074 · SCHEDULE 13G, 2026-08-07
- · Holder: Vanguard Capital Management · Percent: 5.28% · SCHEDULE 13G
- · Reporting person: Vanguard Portfolio Management · Sole voting: 13,581 · Shared voting: 0 · Sole dispositive: 1,773,131 · Shared dispositive: 0 · SCHEDULE 13G, 2026-04-29
Westamerica BanCorp has 6 Schedule 13D or 13G filings on record since 2026-03-27. 3 holders' latest filing reports 5% or more of common stock. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| American Century Investment Management, Inc. | 8.3% | 1,958,072 | SCHEDULE 13G/A, 2026-08-14 | 2026-06-30 |
| Vanguard Portfolio Management | 7.33% | 1,773,131 | SCHEDULE 13G, 2026-04-29 | 2026-03-31 |
| State Street Corporation | 5.9% | 1,394,074 | SCHEDULE 13G, 2026-08-07 | 2026-06-30 |
| Vanguard Capital Management | 4.9% | 1,134,029 | SCHEDULE 13G/A, 2026-10-30 | 2026-09-30 |
| The Vanguard Group | 0% | 0 | SCHEDULE 13G/A, 2026-03-27 | 2026-03-13 |
Holding shares or following this stake? See who's behind Westamerica BanCorp and the warning signs.
Free to see. No signup.
Keep reading
More on Westamerica BanCorp and the records around it.
Westamerica BanCorp elsewhere on the record
Companies that share a holder
- American Century Investment Management, Inc. also filed stake reports on 83 other companies: Visteon Corporation (Oct 2026), MarineMax, Inc. (Sep 2026), AdvanSix Inc. (Aug 2026)
- STATE STREET CORPORATION also filed stake reports on 343 other companies: TRADE DESK INC/THE (Oct 2026), CENTRUS ENERGY CORP (Sep 2026), ACADIA PHARMACEUTICALS INC (Aug 2026)
- Vanguard Portfolio Management also filed stake reports on 941 other companies: Newmark Group Inc (Nov 2026), A10 Networks Inc (Oct 2026), ADT Inc (Oct 2026)
Watch Westamerica BanCorp
Get an email when Westamerica BanCorp files again: a new raise, a leadership change, a layoff or an IPO filing. One email first to confirm; nothing else until you click it. At most one a day, one click to stop. Free for up to 3 companies.
Want the whole picture on Westamerica BanCorp?
Example from a real report (our sample on Target): “The Q2 2026 earnings report, published August 19, 2026, showed adjusted EPS of $2.46 against an expected $2.33” Source: CNBC
A Full Report on Westamerica BanCorp: verified, sourced, every claim cited, ready in a few minutes. See pricing.
What the Full Report on Westamerica BanCorp covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
Sources
6 cited sources found
Plus the sections for what you are deciding, which you pick after ordering.
A real finished report, first screen. Opens in a new tab.
Not ready to order yet? Keep this snapshot.
Sends this preview to you once; we won't add you to any list
Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| American Century Investment Management, Inc. | 1,920,874 | 0 | 1,958,072 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| American Century Companies, Inc. | 1,920,874 | 0 | 1,958,072 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| Stowers Institute for Medical Research | 1,920,874 | 0 | 1,958,072 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| Vanguard Portfolio Management | 13,581 | 0 | 1,773,131 | 0 | SCHEDULE 13G, 2026-04-29 |
| State Street Corporation | 0 | 283,756 | 0 | 1,394,074 | SCHEDULE 13G, 2026-08-07 |
| Vanguard Capital Management | 169,595 | 0 | 1,134,029 | 0 | SCHEDULE 13G/A, 2026-10-30 |
The latest filing identifies Westamerica BanCorp by CUSIP 957090103 and gives its principal executive office as 1108 Fifth Avenue, San Rafael, CA 94901 (SCHEDULE 13G/A, 2026-10-30).
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2026-03-27 | The Vanguard Group | 0% | SCHEDULE 13G/A |
| 2026-04-29 | Vanguard Portfolio Management | 7.33% | SCHEDULE 13G |
| 2026-04-30 | Vanguard Capital Management | 5.28% | SCHEDULE 13G |
| 2026-08-07 | State Street Corporation | 5.9% | SCHEDULE 13G |
| 2026-08-14 | American Century Investment Management, Inc. | 8.3% | SCHEDULE 13G/A |
| 2026-10-30 | Vanguard Capital Management | 4.9% | SCHEDULE 13G/A |
Questions about who owns Westamerica BanCorp
Who owns Westamerica BanCorp?
On this page, 3 holders' latest ownership filings report 5% or more of Westamerica BanCorp: American Century Investment Management, Inc. (8.3%, Schedule 13G/A, filed 2026-08-14), Vanguard Portfolio Management (7.33%, Schedule 13G, filed 2026-04-29) and State Street Corporation (5.9%, Schedule 13G, filed 2026-08-07).
Who are the largest shareholders of Westamerica BanCorp?
By the share each holder's latest filing reports, the largest holders of Westamerica BanCorp on this page are American Century Investment Management, Inc. (8.3%), Vanguard Portfolio Management (7.33%) and State Street Corporation (5.9%).
When did American Century Investment Management, Inc. buy into Westamerica BanCorp?
The filings give report dates, not purchase dates. The earliest filing from American Century Investment Management, Inc. on this page is the Schedule 13G/A, filed 2026-08-14, reporting 8.3%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 6 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Tools for this story
Each opens in a new tab, filled in for Westamerica BanCorp. With no account yet, you sign up free and land on the result.
Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.