"Sonny is a seasoned professional, we know exactly what we are getting with him and we know he won't let us down at this level," said Wales coach Robin McBryde.
"He brings a pedigree and level of experience which is unquestioned and we are fortunate to be able to call on someone of his calibre at short notice.
"James goes to South Africa with whole of Wales behind him, the call-up will be a real dream come true for him and we also know he won't let the Lions down.
"He is a player of mercurial talents and the rugby world will be excited by the prospect of having James Hook on the Lions tour.
"We have obviously lost some of James' versatility in terms of the positions he could cover, but we had selected him primarily as a centre on this tour and we are confident Sonny will be a more than able replacement in that sense.
"Sonny now has a very real chance to re-establish himself on the international scene after an injury lay-off ruled him out for much of 2009."
Commenting on the Hook's selection as a replacement for Leigh Halfpenny, Lions Head Coach Ian McGeechan said, "After analysing our requirements for a replacement as we head to South Africa on Sunday we decided that James was the ideal person to come into the tour squad."
"A very important consideration for us was to strengthen the goal kicking options in the squad. James is an accomplished goal kicker and has scored over 200 points for his country in his 33 appearances. Also, he has played at fly half, centre and fullback for Wales but is also comfortable at outside centre."
"He is very familiar with other backs in the squad having played in the same Welsh team as Mike Phillips, Stephen Jones, Jamie Roberts, Shane Williams and Lee Byrne. Three of these also play in the Ospreys team with him that also includes Tommy Bowe. Therefore there is an existing understanding between all of these players."