Pat's will face a familiar foe in the shape of IBV, Bohs will also be joining their Dublin rivals in Iceland while Sligo face a trip to Slovakia
Sligo Rovers, who enter the competition in the second qualifying round, play Slovakian side Spartak Trnava.
Bohs will play Thor Akureyri while St Pat's will take on IBV for the second year in succession. The Inchicore side defeated their Icelandic counterparts 2-1 on aggregate last season.
Thor Akureyri play their football in the Icelandic second division and qualified for the Europa League qualifying rounds as runners-up in the domestic cup.
Sligo's opponents finished second in the Slovakian top flight last season behind Zilina.
Bohs and St Pat's will play their respective first-round ties on July 5 and July 12.
Sligo go away to Slovakia on July 19 and entertain Trnava at the Showgrounds on July 26.