The Las Vegas callbacks were held at Planet Hollywood Resort and Casino in Las Vegas, Nevada. For the first time in nine seasons, contestants were allowed to choose their own groups for the group choreography round, in contrast to previous seasons where the groups were assigned. With cuts made following each round of choreography, thirty-five contestants remained at the close of the week, prior to the selection of the Top 20.

* Only participated on the judge's panel on the round they choreographed.

In January 2012, Fox announced that So You Think You Can Dance would be returning for its ninth season in a format similar to that seen in season one; a single two-hour episode per week, eliminating each week's results show.^[5] In an interview shortly thereafter, Lythgoe hinted at a format where each week's episode is ended with the revelation of the bottom three couples (based on the votes from the previous week) but after all contestants had performed the new week's routines, giving the judges an additional routine to take into account when deciding which contestants (from amongst the bottom three couples) to save and which to send home for that week. This contrasts with the season one format where judges would nominate a bottom three couples and home viewers would vote out two contestants, the results being pre-taped and shown at the beginning of the next week's episode. Lythgoe also hinted at which elements of the results show were likely to be carried over into the new format, suggesting the group and guest dance routines would be shown priority over guest musical acts.^[6]

These above changes all proved to be in place once the season's performance shows began airing but were also accompanied by a number of other format tweaks. These additional changes most notably include the fact that the season will crown two winners (one female and one male) and that voting for individual contestants (as opposed to couples) began with the first week of the Top 20 competition with 1-855-GO-HIM## for the guys and 1-855-GO-HER## for the girls as opposed to halfway through the performance show phase, as in previous seasons. Additionally there have been tweaks to the format of the "dance for your life" solos, the last chance efforts which contestants are given to impress judges and remain in the competition if the at-home-viewer votes put them in the bottom 6 dancers. In previous seasons, all contestants who were in danger of elimination were automatically assigned to perform such solos but in season 9 the judges, taking into advisement the contestants' previous performances and the advice of the choreographers who have worked with them, will decide each week which (if any) contestants will perform solos. For example, in Week 2, the first week of the competition to feature eliminations (in this case a double elimination), the judges decided which two of the six contestants in danger they wished to save without asking for additional solos. By contrast, in week 3 they decided that Lindsay Arnold and George Lawrence Jr. would be safe without being required to perform a solo but the remaining four dancers were required to perform, with two ultimately eliminated.

The ninth season is also the first in which contestants have been able to exert some control over the styles they dance for their duets; Lythgoe revealed during the week 3 performances that during this season couples are given the ability to pick their styles from the pool of available routines for a given week, with the order of choosing determined by drawing lots. Season 9's Top 14 show also became the first episode in the show's history to feature only one style, the first to feature only one choreographer and the first to feature routines from previous seasons danced by new contestants when it aired as a tribute to long-time contributing choreographer Mia Michaels, with seven of her past contemporary routines danced by season 9 contestants.

Unlike previous seasons, each week's Bottom 6 / Bottom 4 contestants are determined by the previous week's voting. The judge's panel still chooses which of these bottom contestants will be eliminated each week until the Top Ten. However, not all contestants who are in danger of elimination will perform final solos by default; the judges will determine each week which contestants will be asked to perform a "dance for your life" solo, if any. As no voting had been conducted previously, no contestants were eliminated for the Week 1 show; as a result, four contestants were eliminated in the Week 2 show, as opposed to the usual two. No voting took place after the Top 6 performance / Top 4 announcement show. The next week's show (the Top 4 performance finale) was followed by voting, the results of which were announced yet one more week later on the season's grande finale.

  This contestant was eliminated this week.

  This contestant was in the bottom 4 this week.

  These two dancers won the competition.