Lenihan, 20, has been unable to break into the first-team set-up at Hull following his summer switch from Cork.
Hull boss Steve Bruce admits Lenihan needs games and that playing reserve team matches for City is not the way to go.
Lenihan is set to make his debut against Leeds United today and Bruce said: “Brian has gone to Blackpool because he is a young lad who needs to play some games. It is a good move for him.
“The games that we can offer him in the reserve league we are in won’t do him any good.
“To get him out on loan gives him match fitness. It is very difficult for me just to ask a player to train physically hard. They need to go and play games.”
Blackpool boss Lee Clark revealed that he has been an admirer of Lenihan’s for some time — and was interested in signing him before Hull made their move.
“I was watching him before he signed for Hull when I was Birmingham City manager. He’s very attack-minded and he’s got great energy to get up and down the park. I spoke to Steve and since he’s been at Hull he’s been very impressed. We’re going to enjoy working with him.