The Olympic gymnast tweeted to his thousands of followers about Sid Owen's exit from the competition before it aired on Sunday (October 28).
The EastEnders actor was eliminated on Sunday's (October 28) results show, which was filmed immediately after the initial performances on Saturday.
Smith accidentally revealed who had exited the competition on Saturday night, tweeting: "Wat an amazing but emotional roller coaster (sic).
"So much luv for @FlaviaCacace & it's so sad to say bye to @sidowen5 & @The_OlaJordan #crewlove."
The tweet was later deleted after BBC producers contacted Smith about his error, reports The Sun.
Copyright: BBCA BBC source said: "Saturday night can be quite overwhelming and emotional for the celebrities, especially when someone leaves the contest.
"Louis was so caught up in the show that he totally forgot that TV audiences - along with fans who follow him on Twitter - hadn't seen the result.
"Luckily the tweet was noticed quickly and taken down, and the importance of keeping the show result secret has been impressed upon Louis.
"He is embarrassed about it, but at the end of the day it was an honest mistake."
Louis Smith topped the Strictly leaderboard with partner Flavia Cacace after their tango routine to Rihanna's track 'Disturbia'.
Strictly Come Dancing continues on Saturday, November 3 at 6.30pm on BBC One.