The girls shared a smooch after singing the song Anxiety together during Julia's show at the Fonda.
Both Selena, 27, and Julia, 25, posted a photo of the kiss onto their Instagram accounts on Tuesday.
In addition to the kissing photo, the ladies also showed off the matching arrow tattoos they received following their performance.
Posting a photo of the girls admiring the dainty friendship tattoos, Selena wrote on her Instagram stories, 'It's tatted... my arrow points to you forever.'
The delicate arrow tattoos were inscribed below the thumb, and indeed pointed directly at one another when the hands were placed side by side.
The ladies received the matching tattoos directly after their performance on Monday night.
The tattoo artists who inscribed the ink, Brad Reis and London Reese, documented the design process on their Instagram page.
In videos posted to both their accounts, the girls were still backstage as they prepared for the tattoos.
'A point like that with a line, or did you want it to have like a cool triangle?' London asked the girls, who were holding hands.
'Let's do that!' Julia said, before turning to Selena. 'What do you think?'
'Yeah,' the songstress replied.
Brad captioned the video of the girls, 'So last night I got to tattoo @selenagomez while my main brother @londonreese tattooed his bestie @juliamichaels , safe to say last night was super rad and meaningful for me! London your the f**king man and I'll never forget the way you put me on! Going up gang in full effect!'
London was just as effusive in his caption.
'Spent the last couple days celebrating the birth of one of my faves, miss @juliamichaels. Went to her show with @bradreis_tattoo and I tattooed Julia while my dude tattooed the ever so sweet @selenagomez. The vibes were the sickest and both these girls are as dope as you could hope for. Happy birthday, Feej! Love ya, kid!!'
Selena co-wrote her new empowerment track Lose You To Love Me alongside Julia, who is currently on tour.
The pop star surprised audience members at Julia's show Monday night, joining her on stage to sing their song Anxiety.
Julia's tour continues with stops in San Francisco, California, Portland, Oregon, Vancouver, Canada, followed by several shows in Mexico.
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