The former New Zealand Cricket chairman succeeded India's Sharad Pawar at the ICC Annual Conference in Kuala Lumpur, where former South Africa wicket-keeper David Richardson was confirmed as the new ICC chief executive at the end of compatriot Haroon Lorgat's four-year term.
"I believe that the challenges ahead are no less daunting than those we have faced in the last two years if we are to maintain the vibrancy and viability of the three formats of the sport," Isaac said in a statement.
"I look forward to serving the game with honesty and integrity and to the best of my ability. I look forward to handing on the guardianship of the sport with the game enjoying even greater health," he added.
Isaac takes over at a time when the ICC is perceived as too susceptible to the financial might of the Indian cricket board. The governing body's failure to mandate the use of the Decision Review System earlier this week is cited as yet another instance of its helplessness against the Indian board, which has been steadfast in its opposition to the technology.
In the annual conference, the ICC agreed to create the post of an ICC Chairman, who would call the shots, remove the role of ICC vice-president and make the president's role "ceremonial in nature with a term of only one year." The ICC board will select a chairman in 2014 with a two-year term.
New ICC boss defends technology U-turn
World cricket's new chief executive defended an embarrassing U-turn over appeals technology and said he wouldn't drag powerful India "kicking and screaming" into accepting it.
Richardson admitted nearly all players and umpires backed the Decision Review System (DRS), which checks whether batsmen should be given out.
But, signalling a softly-softly approach towards the ICC's richest and most influential member, Richardson said he wouldn't try to force India to lower its staunch opposition to the technology.
The ICC was left red-faced at annual talks this week when chief executives proposed mandatory DRS in Tests and one-day internationals, only for the board to reject the move and leave it as a decision for the two competing sides.
India was the only country to publicly oppose universal use of the ball-tracking and thermal-imaging system, and wields strong influence over the board owing to the revenues from its huge fan-base.
"The point is that the BCCI (Board of Control for Cricket in India) need to make that decision for themselves," Richardson told a press conference. "It's never good to take anyone kicking and screaming to do anything.
"The introduction of technology has always been controversial... but slowly but surely that's changed and I think we're pretty much at that point where everyone is accepting, certainly at international level.
"I don't think (the decision is) negative at all. We'll be seeing DRS used in the majority of series going forward and there would be no sense in forcing anything upon anybody."
The South African took up his post alongside new president Alan Isaac of New Zealand.
The two are tasked with steering the sport through a tricky period as it tries to recover from some damaging spot-fixing scandals and rationalise the demands of its three competing formats.
The ICC has also been urged to implement far-reaching reforms in an independent review which damningly termed the body a "members' club", and recommended a more inclusive board and membership rules.
But talks on the reforms, which are also opposed by India, made little progress in Kuala Lumpur. And Richardson sounded an ominous note when he said nothing would change without the current board's approval.
"The bottom line is the ICC board determines policy for the ICC going forward," Richardson said, although he denied that dealing with India would be his main preoccupation as chief executive.
"I don't think will involve any special negotiations with India," he said.
"A lot is made of that but there are 10 full members and I think our task is a lot more simple and a lot more practical than these high-level talks you might imagine."
The ICC also unveiled a new post of chairman and decided to relegate the presidency to a ceremonial role after Isaac's term finishes in 2014, measures which were "coincidentally" proposed in the independent review, Isaac said.
But Isaac, Richardson and outgoing chief executive Lorgat all warned against expecting quick progress towards the more contentious reforms, which will be discussed at the next board meeting in October.
"I think it would be unfair of any of us to expect overnight change," Lorgat said.
India's deep suspicion of DRS stems from their 2008 Test series with Sri Lanka, when the technology was on trial and a number of reviews went against them.
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