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 | 38 | 29 | 7 | 2 | 89 | 22 | 67 | 94 |
| 2 | AC Milan | 38 | 22 | 9 | 7 | 76 | 49 | 27 | 75 |
| 3 | Juventus | 38 | 19 | 14 | 5 | 54 | 31 | 23 | 71 |
| 4 | Atalanta BCAtalanta | 38 | 21 | 6 | 11 | 72 | 42 | 30 | 69 |
| 5 | Bologna | 38 | 18 | 14 | 6 | 54 | 32 | 22 | 68 |
| 6 | Roma | 38 | 18 | 9 | 11 | 65 | 46 | 19 | 63 |
| 7 | Lazio | 38 | 18 | 7 | 13 | 49 | 39 | 10 | 61 |
| 8 | Fiorentina | 38 | 17 | 9 | 12 | 61 | 46 | 15 | 60 |
| 9 | Torino | 38 | 13 | 14 | 11 | 36 | 36 | 0 | 53 |
| 10 | Napoli | 38 | 13 | 14 | 11 | 55 | 48 | 7 | 53 |
| 11 | Genoa | 38 | 12 | 13 | 13 | 45 | 45 | 0 | 49 |
| 12 | Monza | 38 | 11 | 12 | 15 | 39 | 51 | -12 | 45 |
| 13 | Hellas VeronaHellas Verona | 38 | 9 | 11 | 18 | 38 | 51 | -13 | 38 |
| 14 | Lecce | 38 | 8 | 14 | 16 | 32 | 54 | -22 | 38 |
| 15 | Udinese | 38 | 6 | 19 | 13 | 37 | 53 | -16 | 37 |
| 16 | CagliariCagliari | 38 | 8 | 12 | 18 | 42 | 68 | -26 | 36 |
| 17 | Empoli | 38 | 9 | 9 | 20 | 29 | 54 | -25 | 36 |
| R | FrosinoneFrosinone | 38 | 8 | 11 | 19 | 44 | 69 | -25 | 35 |
| R | SassuoloSassuolo | 38 | 7 | 9 | 22 | 43 | 75 | -32 | 30 |
| R | Salernitana | 38 | 2 | 11 | 25 | 32 | 81 | -49 | 17 |
| > Serie A Full Table | |||||||||
