109 people with their fishing trawler were nabbed by the Navy 25 nautical miles northeast off the coast of Kalmunai in the eastern province, Naval spokesman Kosala Warnakulasuriya said.
There were 101 Tamils and 8 Sinhalese who were heading for Australia, he said.
Another group of 22 people were also arrested for preparing to leave the country illegally at Chilaw in the west coast.
Sri Lankan authorities last week announced that a three tier programme to curb illegal immigration had been implemented.
Police spokesman superintendent Ajith Rohana said over 400 people have now been arrested since end of May.