The decision appears to confirm criticisms that the reality TV show has been a ratings disappointment to the channel.
From 11 June Survivor will be scheduled just once a week on Mondays at 9pm.
Thursday's programme will be dropped and, from 18 June, the interview-based Survivor Unseen will be shown after Tuesday's News at Ten.
ITV's director of programmes David Liddiment said: "Its audience has taken longer than anticipated to build.
"As we move towards Tribal Merger in the show next week and the countdown to the final begins, we are changing the scheduling to give Survivor the best possible chance to grow."
Survivor's first outing was watched by 6.5 million people, but ratings have fallen. On Thursday 31 May just 4.4 million watched model Sarah Odell voted off the island.
Tuesday's audience for Survivor Unseen sank to a new low of just 3.9 million viewers, representing 19.4% of the viewing audience - compared to the usual ITV peaktime share of 37%.
Contrast
When the programme started there were predictions that it might attract 12 million viewers.
By contrast, Channel 4's audience for Big Brother 2 has been growing and has now reached more than four million.
Last week, both Wednesday and Thursday night's episodes attracted more viewers than the BBC's main news bulletin.
Media observers have also noted that the tabloid newspapers have been much more pre-occupied with Big Brother 2 than with Survivor.
Despite the show's ratings, David Liddament defended the programme as "a bold commission for ITV" and said: "I am extremely proud of the show, and it has clearly had impact."