Ferguson expressed his surprise when the veteran defender was named in Roy Hodgson's squad this week, saying Ferdinand had not made up his mind about joining up.
However, the United boss changed his tune after the centre-back laid on the winning goal for Wayne Rooney in the 1-0 Premier League victory over Reading at Old Trafford.
"Rio will be joining up and [England team-mate] Ashley Young should be OK," Ferguson said in a post-match interview.
The 34-year-old Ferdinand was recalled on Thursday after a near two-year absence from the international squad including being left out of Euro 2012.
The defender, who made his debut for England 16 years ago and won the last of his 81 caps in a friendly against Switzerland in June 2011, was snubbed for Euro 2012 in what Hodgson described then as a "footballing decision".
Critics suggested the reason Ferdinand was omitted from the Euro 2012 squad was because of tensions with former England skipper John Terry who was involved in a racism row with Ferdinand's brother Anton.
Terry's subsequent international retirement has left England short of pedigree in the central defensive areas.
United winger Young went off against Reading after being hurt in a challenge with Garath McCleary.
Ferguson's team went 15 points clear at the top of the table after the win.
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