| Cover | Apr. 08, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 8, 2022 |
| Entity File Number | 000-22245 |
| Entity Registrant Name | Seelos Therapeutics, Inc. |
| Entity Central Index Key | 0001017491 |
| Entity Tax Identification Number | 87-0449967 |
| Entity Incorporation, State or Country Code | NV |
| Entity Address, Address Line One | 300 Park Avenue |
| Entity Address, Address Line Two | 2nd Floor |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10022 |
| City Area Code | (646) |
| Local Phone Number | 293-2100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.001 par value |
| Trading Symbol | SEEL |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
