It was a close result between the two shows but Gary's BBC One series edged out its ITV rival.
Let It Shine premiered to an audience of 6.3 million viewers between 7PM and 8:25PM, peaking with 6.8 million.
The Voice UK, which used to air on BBC One, made its debut on ITV for series six with its least watched launch to date.
An average of 6 million viewers (including ITV+1) tuned in between 8PM and 9:35PM for the opening round of blind auditions, down 1.1 million viewers on last year's series launch.
The Voice UK however did achieve a slightly higher peak audience than Let It Shine with a high of 6.9 million viewers.
It was of course only the first episode for both series, which return to TV for their second respective instalments next Saturday night.
The Voice UK Launch ratings
2012 - 8.4 million
2013 - 6.2 million
2014 - 8.4 million
2015 - 8.1 million
2016 - 7.1 million
2017 - 6.0 million
Let It Shine was the night's most watched programme, with Pointless beforehand scoring 5.3 million and Casualty afterwards seen by 4.6 million. New BBC One drama Taboo started with 4.8 million viewers.
On ITV, Ninja Warrior UK bounced back from last week's series opener of 2.1 million viewers - an all time low for the show - to a healthy 3.4 million, up 200,000 viewers on 2016's equivalent episode.
After The Voice UK at 9:25PM, Through the Keyhole with Keith Lemon had 2.9 million viewers.
Elsewhere, Celebrity Big Brother's latest highlights on Channel 5 at 9PM had just over 1 million viewers.