The 2009–10 Danish 1st Division season was the 14th season of the Danish 1st Division league championship, governed by the Danish Football Association.
The division-champion, AC Horsens, and runners-up, Lyngby BK, were promoted to the 2010–11 Danish Superliga. The teams in the 14th, 15th and 16th places, Thisted FC, BK Frem and Brabrand IF, were relegated to either 2nd Division East or West, based on their respective locations.
| Club | Finishing position last season | First season of current spell in 1st Division | |
|---|---|---|---|
| AB | 3rd | 2004–05 | |
| AC Horsens | 12th in Superliga | 2009–10 | |
| BK Frem | 11th | 2004–05 | |
| Brabrand IF | 3rd in 2nd Division West | 2009–10 | |
| FC Fredericia | 7th | 2001–02 | |
| FC Fyn | 1st in 2nd Division West | 2009–10 | |
| FC Roskilde | 10th | 2008–09 | |
| FC Vestsjælland | 1st in 2nd Division East | 2009–10 | |
| Hvidovre IF | 8th | 2007–08 | |
| Kolding FC | 12th | 2005–06 | |
| Lyngby BK | 6th | 2008–09 | |
| Næstved BK | 5th | 2006–07 | |
| Skive IK | 13th | 2007–08 | |
| Thisted FC | 9th | 2008–09 | |
| Vejle BK | 11th in Superliga | 2009–10 | |
| Viborg FF | 4th | 2008–09 |
| Team | Outgoing manager | Manner of departure | Date of vacancy | Replaced by | Date of appointment | Position in table | |
|---|---|---|---|---|---|---|---|
| Vejle BK | Lasse Christensen | End of tenure as caretaker | 30 June 2009 |  Mats Gren | 1 July 2009[1] | Pre-Season | |
| AC Horsens | Henrik Jensen | Sacked | 30 June 2009[2] | Johnny Mølby | 1 July 2009[3] | Pre-Season | |
| Viborg FF | Søren Frederiksen | Stepped down | 30 June 2009[4] | Lars Søndergaard | 1 July 2009[5] | Pre-Season | |
| BK Frem | Anders Theil | Mutual consent | 30 June 2009 | Christian Andersen | 1 July 2009[6] | Pre-Season | |
| Kolding FC | Frank Andersen | Mutual consent | 9 September 2009[7] | Jens Letort | 10 September 2009[8] | 14th |