The 25-year-old's previous deal with the Blues had been due to expire in 2017.
However, the defender, who scored the only goal of the game in Empoli's 1-0 win over Lazio at the weekend, has now agreed a two-year extension.
Former Italy Under-21 international Tonelli has risen through the ranks at the Stadio Carlo Castellani, having made his debut in 2010.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| C | Inter Milan | 35 | 28 | 5 | 2 | 81 | 19 | 62 | 89 |
| 2 | AC Milan | 35 | 21 | 8 | 6 | 67 | 42 | 25 | 71 |
| 3 | Juventus | 35 | 18 | 12 | 5 | 48 | 27 | 21 | 66 |
| 4 | Bologna | 35 | 17 | 13 | 5 | 49 | 27 | 22 | 64 |
| 5 | Atalanta BCAtalanta | 34 | 18 | 6 | 10 | 63 | 38 | 25 | 60 |
| 6 | Roma | 35 | 17 | 9 | 9 | 62 | 42 | 20 | 60 |
| 7 | Lazio | 35 | 17 | 5 | 13 | 45 | 37 | 8 | 56 |
| 8 | Napoli | 35 | 13 | 12 | 10 | 53 | 44 | 9 | 51 |
| 9 | Fiorentina | 34 | 14 | 8 | 12 | 51 | 39 | 12 | 50 |
| 10 | Torino | 35 | 11 | 14 | 10 | 31 | 31 | 0 | 47 |
| 11 | Monza | 35 | 11 | 12 | 12 | 38 | 46 | -8 | 45 |
| 12 | Genoa | 35 | 10 | 13 | 12 | 41 | 43 | -2 | 43 |
| 13 | Lecce | 35 | 8 | 13 | 14 | 32 | 50 | -18 | 37 |
| 14 | Hellas VeronaHellas Verona | 35 | 8 | 10 | 17 | 33 | 46 | -13 | 34 |
| 15 | CagliariCagliari | 35 | 7 | 12 | 16 | 37 | 60 | -23 | 33 |
| 16 | FrosinoneFrosinone | 35 | 7 | 11 | 17 | 43 | 63 | -20 | 32 |
| 17 | Empoli | 35 | 8 | 8 | 19 | 26 | 50 | -24 | 32 |
| 18 | Udinese | 35 | 4 | 18 | 13 | 33 | 52 | -19 | 30 |
| 19 | SassuoloSassuolo | 35 | 7 | 8 | 20 | 41 | 70 | -29 | 29 |
| R | Salernitana | 35 | 2 | 9 | 24 | 27 | 75 | -48 | 15 |
| > Serie A Full Table | |||||||||
