The Colombian international, 27, spent the second half of the 2013-14 campaign on loan at West Ham United.
"I'll be joining a great team," Armero told Milan's official television channel. "I want to find my place here and do well."
Following their eighth-place finish in the Serie A table last season, Milan have signed 14 new players ahead of the new campaign.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| C | Inter Milan | 36 | 29 | 5 | 2 | 86 | 19 | 67 | 92 |
| 2 | AC Milan | 36 | 22 | 8 | 6 | 72 | 43 | 29 | 74 |
| 3 | Bologna | 36 | 18 | 13 | 5 | 51 | 27 | 24 | 67 |
| 4 | Juventus | 36 | 18 | 13 | 5 | 49 | 28 | 21 | 67 |
| 5 | Atalanta BCAtalanta | 35 | 19 | 6 | 10 | 65 | 39 | 26 | 63 |
| 6 | Roma | 36 | 17 | 9 | 10 | 63 | 44 | 19 | 60 |
| 7 | Lazio | 36 | 18 | 5 | 13 | 47 | 37 | 10 | 59 |
| 8 | Fiorentina | 35 | 15 | 8 | 12 | 53 | 40 | 13 | 53 |
| 9 | Napoli | 36 | 13 | 12 | 11 | 53 | 46 | 7 | 51 |
| 10 | Torino | 36 | 12 | 14 | 10 | 33 | 32 | 1 | 50 |
| 11 | Genoa | 36 | 11 | 13 | 12 | 43 | 44 | -1 | 46 |
| 12 | Monza | 36 | 11 | 12 | 13 | 39 | 48 | -9 | 45 |
| 13 | Lecce | 36 | 8 | 13 | 15 | 32 | 52 | -20 | 37 |
| 14 | Hellas VeronaHellas Verona | 36 | 8 | 10 | 18 | 34 | 48 | -14 | 34 |
| 15 | Udinese | 36 | 5 | 18 | 13 | 35 | 52 | -17 | 33 |
| 16 | CagliariCagliari | 36 | 7 | 12 | 17 | 38 | 65 | -27 | 33 |
| 17 | FrosinoneFrosinone | 36 | 7 | 11 | 18 | 43 | 68 | -25 | 32 |
| 18 | Empoli | 36 | 8 | 8 | 20 | 26 | 52 | -26 | 32 |
| 19 | SassuoloSassuolo | 36 | 7 | 8 | 21 | 42 | 72 | -30 | 29 |
| R | Salernitana | 36 | 2 | 10 | 24 | 28 | 76 | -48 | 16 |
| > Serie A Full Table | |||||||||
