| Cover Page Cover Page | Jul. 23, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jul. 23, 2020 |
| Entity Registrant Name | GENOCEA BIOSCIENCES, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36289 |
| Entity Tax Identification Number | 51-0596811 |
| Entity Address, Address Line One | 100 Acorn Park Drive |
| Entity Address, Address Line Two | 5th Floor |
| Entity Address, City or Town | Cambridge |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02140 |
| City Area Code | 617 |
| Local Phone Number | 876-8191 |
| 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 per share |
| Trading Symbol | GNCA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001457612 |
| Amendment Flag | false |
