Parkinson conceded there had been "an air of negativity" hanging over the club following last week's sale of leading goalscorer Nahki Wells to Huddersfield.
But former Peterborough forward McLean, 30, has signed a two-and-a-half year contract with the club following his arrival from Hull and Parkinson feels it is a statement of intent.
"It lifts the whole squad and it lifts the fans and that's important because Nahki had been an integral part of the success we've had," Parkinson told Press Association Sport.
"Nobody wanted Nahki to go, there was an acceptance that at some point he was going to go, so it was important the striker we brought in was the right one and I do feel we've got the right one."
McLean is expected to make his debut at Sheffield United on Saturday, while Parkinson is satisfied the £1.3million received for Wells will be put to good use.
"The money we got from the sale of Nahki, the chairmen aren't going to split it and go on holiday, they're going to utilise it for the club going forward," said Parkinson.
The Bantams boss hinted at a possible search for a new defender as cover for James Meredith, who will be sidelined for six weeks after breaking a bone in his foot.
Parkinson added: "We've used the money to bring in Aaron and there may be one or two more things as we go along this month and then in the summer we will have a budget that is competitive at this level."