Tendulkar, 33, will be deputy to skipper Rahul Dravid for the one-day series against the West Indies starting on Sunday amid speculation that he may even be named Indian captain after the World Cup.
The unexpected appointment comes at a time when the master batsman is struggling to regain top form after a spate of injuries that threatened to end a glorious 17-year career.
Tendulkar acceptance of vice-captaincy was indeed a strange decision. Why has Sachin accepted the irregular offering at the age of 34, when critics have begun to question not just his non-match-winning skills but also on his very selection in the team?
Tendulkar averaged just 33.16 in three Test matches and 23.25 in four one-day internationals on the recent tour of South Africa, a far cry from his lofty record-setting standards.
The selectors, however, chose to keep faith in him even as Test vice-captain Venkatsai Laxman and one-day deputy Virender Sehwag were dumped for the first two one-dayers against the West Indies.
Chairman of selectors Dilip Vengsarkar said he made Tendulkar vice-captain because someone who is experienced and also sure of his place in the playing eleven was needed to "guide Rahul Dravid in the important season ahead."
"I offered the post (vice-captaincy) to Sachin and he agreed after giving the proposal some thought," said Vengsarkar, a former India captain and batting great.
Tendulkar voluntarily gave up the task of donning the role of captaincy six years ago when he was in his peak as a batsman and player as he could not take the pressure. Also sadly, while he remained a batting marvel, as a leader he proved to be a comical pip-squeak, tentative, confused and constantly sullen-faced.
Tendulkar led India in 25 Tests and 73 one-dayers between 1996 and 2000 before he voluntarily stepped down, acknowledging his own limitations, after a home series against South Africa.
Tendulkar, who turns 34 on the day of the first World Cup semi-final in Jamaica on April 24, dismissed media speculation he may be named captain after the World Cup.
"At the moment the World Cup is the top priority," he said in a recent interview. "No one has consulted me nor have I discussed with anyone about taking over as Indian captain after the World Cup.
"It is too early to say anything right now. Of course, the selectors have named me as vice-captain. I was consulted about it and I have agreed."
It has also been suggested that Tendulkar was elevated so that former captain Sourav Ganguly, who has made a comeback in both Test and one-day cricket, could be kept away from the team management.
"I will not react to such nonsense," said Vengsarkar. "My job is to see that we field the best team for the World Cup, nothing else matters."
Tendulkar is the world's leading one-day batsman with 14,537 runs from 374 matches with an incredible 40 centuries and 74 fifties.
The Indian is almost 3,000 runs ahead of second-placed Inzamam-ul-Haq of Pakistan (11,591 runs) and has 17 more centuries than his nearest challenger Sanath Jayasuriya of Sri Lanka (23).
But millions of fans have been frustrated in recent months by Tendulkar's inconsistent form and his failure to play match-winning innings as in the past.
In his last 10 Test matches, Tendulkar has managed just 387 runs at 25.80 without adding to his 35 centuries.
His one-day form is even worse, plodding to 248 runs at 24.80.
Tendulkar's backers argue that as he nears 34 he cannot be expected to play the blazing knocks he did as a youngster.
Try telling that to Inzamam, who turns 37 in March, or Jayasuriya and West Indian captain Brian Lara, who will both turn 38 this year.
ThatsCricket (with inputs from Agencies)