Sales kept growing in October and November after rising by 4.9 percent to 152.6 million in the three months from July to September, it said.
Jumbo, which operates 53 department stores in Greece and 20 in Cyprus, Bulgaria and Romania, said first-quarter net profit rose to 21.8 million euros from 20 million euros in the same period last year.
This was despite an increase in corporate taxation to 29 percent from 26 percent this year, part of reforms the Greek government agreed with its international lenders under a third bailout clinched this summer.
Jumbo said robust sales growth in Cyprus, Bulgaria and Romania and a slight improvement in gross profit margin helped it grow its profit.
The company did not say in its statement whether the performance in the first quarter would prompt a revision of its full-year forecasts.
Jumbo had said last month it expected a 15-25 percent drop in net profit in the 12 months to June 2016 due to higher taxation and its impact on costs.