| Club: | Middlesbrough |
| Season: | 1990–91 |
| Manager: | Colin Todd |
| Chairman: | Colin Henderson |
| Stadium: | Ayresome Park |
| League: | Second Division |
| League Result: | 7th |
| Cup1: | FA Cup |
| Cup1 Result: | Fourth round |
| Cup2: | League Cup |
| Cup2 Result: | Fourth round |
| Cup3: | Full Members' Cup |
| Cup3 Result: | Second round |
| League Topscorer: | Slaven (16) |
| Season Topscorer: | Slaven (19) |
| Prevseason: | 1989–90 |
| Nextseason: | 1991–92 |
During the 1990–91 English football season, Middlesbrough F.C. competed in the Football League Second Division.
In the 1990–91 season, Boro finished 7th in the Second Division on goal difference, qualifying for the end of season play-offs. However, they lost in the semifinals of the playoffs against Notts County.
Appearance and goalscoring records for all the players who were in the Middlesbrough F.C. first team squad during the 1990–91 season.[1]
|}
| Date | Player | Previous Club | Fee | |
|---|---|---|---|---|
| July 1990 | John Hendrie | Leeds United | £568,000 | |
| July 1990 | Robbie Mustoe | Oxford United | £396,000 | |
| July 1990 | John Wark | Ipswich Town | Free | |
| July 1990 |  Martin Russell | Scarborough | Free | |
| January 1991 | Colin Walsh | Charlton Athletic | Loan | |
| February 1991 | Andy Dibble | Manchester City | Loan |
| Date | Player | New Club | Fee | |
|---|---|---|---|---|
| July 1990 | Mark Brennan | Manchester City | £500,000 | |
| July 1990 | Peter Davenport | Sunderland | £394,000 | |
| October 1990 | Mark Burke | Wolves | Loan | |
| March 1991 | Mark Burke | Wolves | £32,000 | |
| January 1990 | Kevin Poole | Hartlepool United | Loan |
Notts County won 2–1 on aggregate.
See main article: 1990-91 FA Cup.
See main article: 1990–91 Football League Cup.
See main article: 1990–91 Full Members' Cup.