The 18-year-old is spending the current campaign on loan with Championship side Ipswich, and the forward showed off his abilities - which proved important for Arsenal's under-21 side last season - with a curling shot in the 60th minute at Fratton Park.
With the visitors trailing by two goals, Maitland-Niles latched onto a loose ball in midfield before weaving his way into space and firing a powerful effort into the top corner.
Although his goal was only a consolation one on the night, it will certainly inject the 18-year-old with confidence following his rise through Arsenal's ranks.
Maitland-Niles remains the second-youngest player, behind Jack Wilshere, to have represented the Gunners in the Champions League after coming on as a substitute against Galatasaray in December 2014.
He then made his Premier League debut against Newcastle United just four days later, and has been an ever-present member of Arsenal's Uefa Youth League side since then.
<blockquote class="twitter-tweet" lang="en"> <p dir="ltr" lang="en">.<a rel="nofollow" target="_blank" href="https://twitter.com/Arsenal" class="body-link" data-vars-item-name="BL-3161306-https://twitter.com/Arsenal" data-vars-event-id="c23">@Arsenal</a> loanee <a rel="nofollow" target="_blank" href="https://twitter.com/Ains_7" class="body-link" data-vars-item-name="BL-3161306-https://twitter.com/Ains_7" data-vars-event-id="c23">@Ains_7</a> curls a beauty into the top corner for <a rel="nofollow" target="_blank" href="https://twitter.com/Official_ITFC" class="body-link" data-vars-item-name="BL-3161306-https://twitter.com/Official_ITFC" data-vars-event-id="c23">@Official_ITFC</a>. <a rel="nofollow" target="_blank" href="https://twitter.com/hashtag/EmiratesFACup?src=hash" class="body-link" data-vars-item-name="BL-3161306-https://twitter.com/hashtag/EmiratesFACup?src=hash" data-vars-event-id="c23">#EmiratesFACup</a> <a rel="nofollow" target="_blank" href="https://t.co/U6RYkxyrlx" class="body-link" data-vars-item-name="BL-3161306-https://t.co/U6RYkxyrlx" data-vars-event-id="c23">https://t.co/U6RYkxyrlx</a> — BT Sport Football (@btsportfootball) <a rel="nofollow" target="_blank" href="https://twitter.com/btsportfootball/status/689730354039513090" class="body-link" data-vars-item-name="BL-3161306-https://twitter.com/btsportfootball/status/689730354039513090" data-vars-event-id="c23">January 20, 2016</a>
