| Document and Entity Information | May 03, 2024 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001913971 |
| Current Fiscal Year End Date | --12-31 |
| Document Type | 8-K |
| Document Period End Date | May 03, 2024 |
| Entity Registrant Name | PRINCETON BANCORP, INC. |
| Entity Incorporation State Country Code | PA |
| Entity File Number | 001-41589 |
| Entity Tax Identification Number | 88-4268702 |
| Entity Address, Address Line One | 183 Bayard Lane |
| Entity Address, City or Town | Princeton |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 08540 |
| City Area Code | (609) |
| Local Phone Number | 921-1700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common stock, no par value |
| Trading Symbol | BPRN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
