| Document and Entity Information | Apr. 16, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 16, 2021 |
| Entity Registrant Name | CITIZENS FINANCIAL SERVICES, INC. |
| Entity Incorporation, State or Country Code | PA |
| Entity File Number | 000-13222 |
| Entity Tax Identification Number | 23-2265045 |
| Entity Address, Address Line One | 15 S Main St |
| Entity Address, City or Town | Mansfield |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 16933 |
| City Area Code | 570 |
| Local Phone Number | 662-0444 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000739421 |
