Niall started out in the Tividale FC Academy, before moving to EFL League Two side Morecambe in March 2015, originally signing scholarship forms.
In the summer of 2017, Maher signed his first professional contract with Morecambe after progressing through the U18 setup at the Shrimps, becoming their third choice keeper in the process.
In August 2017, Maher went on a month loan to Northern Premier League Premier Division side Halesowen Town making two appearances for the Yeltz and at the end of his loan, he returned to Morecambe.
In the summer of 2018, Maher was released by Morecambe where he made no first-team appearances and signed for Southern League Premier Division Central side Stourbridge, where he made 10 appearances during the 2018-2019 season.
In August 2019, Maher signed for the Seagulls.