The 32-year-old, who left Hamburger SV at the end of last season, had been widely tipped with a switch to the La Liga club.
Van der Vaart has now officially completed his move to Los Verdiblancos on what is thought to be a three-year deal.
Betis won promotion from the Spanish Segunda Division in 2014-15, finishing five-points clear of third-place Girona.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Barcelona | 17 | 12 | 2 | 3 | 50 | 19 | 31 | 38 |
| 2 | Real Madrid | 17 | 11 | 4 | 2 | 37 | 16 | 21 | 37 |
| 3 | Atletico MadridAtletico | 16 | 10 | 5 | 1 | 30 | 11 | 19 | 35 |
| 4 | Athletic Bilbao | 17 | 9 | 5 | 3 | 26 | 15 | 11 | 32 |
| 5 | Mallorca | 18 | 8 | 3 | 7 | 18 | 21 | -3 | 27 |
| 6 | Villarreal | 15 | 7 | 5 | 3 | 27 | 25 | 2 | 26 |
| 7 | Osasuna | 17 | 6 | 7 | 4 | 22 | 25 | -3 | 25 |
| 8 | Real Sociedad | 16 | 7 | 3 | 6 | 16 | 11 | 5 | 24 |
| 9 | GironaGirona | 17 | 6 | 4 | 7 | 23 | 25 | -2 | 22 |
| 10 | Sevilla | 17 | 6 | 4 | 7 | 18 | 23 | -5 | 22 |
| 11 | Real BetisBetis | 16 | 5 | 6 | 5 | 18 | 20 | -2 | 21 |
| 12 | Celta Vigo | 17 | 6 | 3 | 8 | 25 | 28 | -3 | 21 |
| 13 | Rayo Vallecano | 16 | 5 | 5 | 6 | 18 | 19 | -1 | 20 |
| 14 | Las PalmasLas Palmas | 16 | 5 | 3 | 8 | 22 | 27 | -5 | 18 |
| 15 | Getafe | 16 | 3 | 7 | 6 | 11 | 13 | -2 | 16 |
| 16 | AlavesAlaves | 16 | 4 | 3 | 9 | 18 | 27 | -9 | 15 |
| 17 | Leganes | 16 | 3 | 6 | 7 | 14 | 23 | -9 | 15 |
| 18 | Espanyol | 16 | 4 | 2 | 10 | 15 | 28 | -13 | 14 |
| 19 | Real ValladolidValladolid | 17 | 3 | 3 | 11 | 12 | 34 | -22 | 12 |
| 20 | Valencia | 15 | 2 | 4 | 9 | 13 | 23 | -10 | 10 |
| > La Liga Full Table | |||||||||
