| Club: | San Lorenzo de Almagro |
| Season: | 2017–18 |
| Manager: | Diego Aguirre (until 22 September 2017) Claudio Biaggio (int.) (from 22 September 2017 to 6 December 2017) Claudio Biaggio (from 7 December 2017) |
| Chairman: | Matías Lammens |
| Stadium: | Estadio Pedro Bidegain |
| League: | Primera División |
| League Result: | 2nd |
| Cup1: | 2016–17 Copa Argentina |
| Cup1 Result: | Round of 32 |
| Cup2: | 2017–18 Copa Argentina |
| Cup2 Result: | Round of 64 |
| Cup3: | Copa Libertadores |
| Cup3 Result: | Quarter-finals |
| Cup4: | Copa Sudamericana |
| Cup4 Result: | First stage |
| League Topscorer: | Nicolás Blandi (8) |
| Season Topscorer: | Nicolás Blandi (8) |
| Pattern La1: | _sl2018h |
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| Pattern So1: | _sanlorenzo17h |
| Leftarm1: | 172442 |
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| Prevseason: | 2016–17 |
| Nextseason: | 2018–19 |
The 2017–18 season is San Lorenzo de Almagro's 33rd consecutive season in the top-flight of Argentine football. The season covers the period from 1 July 2017 to 30 June 2018.
.[1]
| Date | Pos. | Name | From | Fee | |
|---|---|---|---|---|---|
| 1 July 2017 | DF |  Víctor Salazar | Rosario Central | Undisclosed[2] [3] | |
| 9 July 2017 | DF | Gonzalo Rodríguez |  Fiorentina | Undisclosed | |
| 10 July 2017 | MF | Alexis Castro | Tigre | Undisclosed | |
| 17 July 2017 | MF | Gabriel Gudiño | Atlético de Rafaela | Undisclosed |
| Date | Pos. | Name | To | Fee | |
|---|---|---|---|---|---|
| 1 July 2017 | MF | Federico Bruno | Bragado | Undisclosed | |
| 1 July 2017 | DF | Rodrigo Tapia | Palestino | Undisclosed[4] | |
| 11 July 2017 | FW | Gonzalo Bergessio | Vélez Sarsfield | Undisclosed | |
| 17 July 2017 | DF | Gonzalo Prósperi | San Martín | Undisclosed | |
| 20 July 2017 | MF | Néstor Ortigoza | Olimpia | Undisclosed | |
| 1 August 2017 | DF | Mathías Corujo | Peñarol | Undisclosed[5] |
| Date from | Date to | Pos. | Name | To | |
|---|---|---|---|---|---|
| 1 July 2017 | 30 June 2018 | FW | Rodrigo Contreras | Arsenal de Sarandí | |
| 6 July 2017 | 30 June 2018 | DF | Alejandro Melo | Atlético Tucumán | |
| 22 July 2017 | 31 December 2017 | FW | Ezequiel Montagna | Temperley | |
| 25 July 2017 | 30 June 2018 | DF | Tomás Cardona | Godoy Cruz | |
| 27 July 2017 | 30 June 2018 | MF | Rodrigo De Ciancio | Temperley |
See main article: article and 2017–18 Argentine Primera División.
See main article: article and 2016–17 Copa Argentina.
See main article: article and 2017 Copa Libertadores.
See main article: article and 2018 Copa Sudamericana.