The appointment of Ptasznik is seen as a coup for Nasdaq, which is looking to expand its footprint in Canada.
Nasdaq announced in March that it plans to seek regulatory approval to turn its existing alternative trading systems in Canada, which are more lightly regulated than exchanges, into full-blown stock exchanges, enabling it to rival the TSX.
Ptasznik, who became TMX CFO in 2000 and oversaw events including the company's initial public offering, will join Nasdaq from July 11.
Frank DiLiso, vice president of corporate finance and administration, has been named interim CFO by TMX while Nasdaq said Ronald Hassen, senior vice president and interim CFO, will remain with the company in an advisory capacity.
TMX shares were down 2.9 percent at C$52 in late morning trading.
Reporting by Amrutha Gayathri in Bengaluru; Editing by Sriraj Kalluvila and Shounak Dasgupta