The One Direction singer has been dating Eleanor Calder since September last year, and told The Sun he was worried about how her family would perceive him.
Tomlinson said: "I was worried about my reputation at first. I remember I sent Eleanor's mum a few text messages saying, 'Please don't judge me thinking I'm like the stereotypical boyband type who is going to go around and sleep with everything that moves'.
"I was trying to convince her I'm quite a good lad but I didn't really need to. Her family are really cool actually, and very understanding of the situation.
"It's important for me to treat a girlfriend with respect."
Earlier this year, Tomlinson hit back at rumours he is romantically involved with bandmate Harry Styles, saying they are "hard to deal with" because of his relationship with Calder.
Watch One Direction's music video for 'Live While We're Young' below: