A 25th-minute goal from the Middlesbrough striker means Boro have now won their first home game in five Championship matches.
Middlesbrough beat Hull City 1-0 on Saturday to rekindle their hopes of finishing in the play-off places in the Championship.
Coming into this game, Boro had won none of their last four games at home in the Championship, putting in serious jeopardy their homes of being in the top six come the end of May.
While they didn’t start the game in exciting fashion, Boro were ahead on the half-hour mark as Britt Assombalonga poked in an Ashley Fletcher cross.
Even after they had gotten the lead, Middlesbrough were unable to get their foothold in the game and it looked as if it was a matter of time before Hull City got back into the game.
However, despite making the lion’s share of chances – one of which hit the woodwork late on in the game – the Tigers were unable to score an equaliser.
Assombalonga's goal helped Boro gain confidence and manager Pulis built on that as his formation change allowed the home side to finish the half on a high.
After the break, Hull started the game as they had started the first half and were left wondering how they weren’t on equal terms after Fraizer Campbell missed a sitter past the half-hour mark.
On the other side, Boro also had their chances to put the game to bed though Assombalonga messed up his pass when he had only the Hull City goalkeeper to beat.
In the final stages of the game, the referee waved away a strong penalty claim from Fraizer Campbell, after which a free-kick from Grosicki hit the bar for the away side.
The Spanish defender had to leave the pitch as he crashed onto the turf 10 minutes into the 2nd half after a tussle with Hull striker Fraizer Campbell.
Speaking after the game, manager Tony Pulis claimed that the defender has suffered a knee injury and was taken to the hospital.
"We're pretty concerned with Dani," he said. "He's gone off to the hospital so we'll see what the situation is."
"It's his knee. I think it was the landing, not the challenge."