| Cover Page | Jun. 30, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Entity Registrant Name | CASTELLUM, INC. |
| Entity Central Index Key | 0001877939 |
| Entity File Number | 001-41526 |
| Entity Tax Identification Number | 27-4079982 |
| Document Period End Date | Jun. 30, 2023 |
| Entity Incorporation, State or Country Code | NV |
| Entity Address, Address Line One | 3 Bethesda Metro Center |
| Entity Address, Address Line Two | Suite 700 |
| Entity Address, City or Town | Bethesda |
| Entity Address, State or Province | MD |
| Entity Address, Postal Zip Code | 20814 |
| City Area Code | 301 |
| Local Phone Number | 961-4895 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.0001 per share |
| Trading Symbol | CTM |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
