He won the NYSAC World Light Heavyweight Title by beating Lou Scozza on February 10, 1930 in Broadway Auditorium. Slattery lost the title later that year in a bout at Bison Stadium against Maxie Rosenbloom for the NYSAC World Light Heavyweight Title and the Undisputed World Light Heavyweight Title. The verdict was "highly unpopular" with the 15,000 fans at the fight.
He secured the NYSAC World Light Heavyweight Championship by defeating Lou Scozza on February 10, 1930 in Broadway Auditorium. Slattery subsequently lost the title that year to Maxie Rosenbloom at Bison Stadium for both the NYSAC World Light Heavyweight Title and the Undisputed World Light Heavyweight Title, with a verdict that was "highly unpopular" among the 15,000 fans present.