Dr. Fellegi joined Statistics Canada, then the Dominion Bureau of Statistics, in 1957 shortly after his arrival in Canada. He was appointed as Chief Statistician of Canada in 1985. Statistics Canada has been recognized as the top statistical office in the world and this recognition is largely due to Dr Fellegi's leadership. He has always emphasized the importance of sound methodology and integrity from his staff. He has contributed greatly to the development and advancement of statistics in Canada, as leader of the national statistical agency, a promoter of research, and supporter of collaboration with statisticians in universities.

Dr Fellegi's outstanding research contributions include work on design of multi-stage rotating panel surveys, response variance, automatic editing and imputation, record linkage, and statistical confidentiality. Two of his papers, on the theory of record linkage and on a systematic approach to automatic edit and imputation, are listed among 19 landmark papers in survey statistics by the International Association of Survey Statisticians. Dr Fellegi has been honoured in many ways, including five honorary doctorates. He is an Officer of the Order of Canada, a Member of the Hungarian Academy of Sciences, and a Gold Medalist of the Statistical Society of Canada. He served as President of the Statistical Society of Canada, the International Statistical Institute, and the International Association of Survey Statisticians.