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 | |
| 1 | Inter Milan | 33 | 27 | 5 | 1 | 79 | 18 | 61 | 86 |
| 2 | AC Milan | 33 | 21 | 6 | 6 | 64 | 39 | 25 | 69 |
| 3 | Juventus | 33 | 18 | 10 | 5 | 47 | 26 | 21 | 64 |
| 4 | Bologna | 33 | 17 | 11 | 5 | 48 | 26 | 22 | 62 |
| 5 | Roma | 33 | 17 | 7 | 9 | 59 | 39 | 20 | 58 |
| 6 | Atalanta BCAtalanta | 32 | 16 | 6 | 10 | 59 | 37 | 22 | 54 |
| 7 | Lazio | 33 | 16 | 4 | 13 | 42 | 35 | 7 | 52 |
| 8 | Napoli | 33 | 13 | 10 | 10 | 50 | 41 | 9 | 49 |
| 9 | Fiorentina | 32 | 13 | 8 | 11 | 45 | 36 | 9 | 47 |
| 10 | Torino | 33 | 11 | 13 | 9 | 31 | 29 | 2 | 46 |
| 11 | Monza | 33 | 11 | 10 | 12 | 35 | 43 | -8 | 43 |
| 12 | Genoa | 33 | 9 | 12 | 12 | 35 | 40 | -5 | 39 |
| 13 | Lecce | 33 | 8 | 11 | 14 | 30 | 48 | -18 | 35 |
| 14 | CagliariCagliari | 33 | 7 | 11 | 15 | 36 | 56 | -20 | 32 |
| 15 | Hellas VeronaHellas Verona | 33 | 7 | 10 | 16 | 31 | 44 | -13 | 31 |
| 16 | Empoli | 33 | 8 | 7 | 18 | 26 | 48 | -22 | 31 |
| 17 | Udinese | 33 | 4 | 16 | 13 | 31 | 50 | -19 | 28 |
| 18 | FrosinoneFrosinone | 33 | 6 | 10 | 17 | 40 | 63 | -23 | 28 |
| 19 | SassuoloSassuolo | 33 | 6 | 8 | 19 | 39 | 65 | -26 | 26 |
| 20 | Salernitana | 33 | 2 | 9 | 22 | 26 | 70 | -44 | 15 |
| > Serie A Full Table | |||||||||
