City arrived at St James' Park on Monday night on the back of two wins and two draws following their return to the Championship, but Danny Guthrie's 52nd-minute goal ended their unbeaten run and sent the Magpies to the top of the table.
Pearson, who spent 16 months at Newcastle and had two spells as their caretaker manager, said: "We have still had a relatively decent start.
"This is disappointing but we have to put it into perspective. We will debrief on the game and then get on with preparing for the next one."
Pearson felt Leicester could have won the game had they not lacked a cutting-edge in front of goal, he added: "We could have got something out of the game had we taken our chances. We expected to get something and we thought we could come here and win.
"It wasn't a brilliant game, both sides turned the ball over too many times, but I don't think there was a lot in the game."