Dennis was born in Berlin on May 19, 1948, the son of Eugene and Leone (Seman) Jackowski. He attended elementary schools in Princeton and Markesan, graduated from Markesan High School in 1966 and MATC in 1968. On October 2, 1971, he was united in marriage to Susan Moderow at St. John's Lutheran Church in Markesan.

Dennis enjoyed working in sales at International Harvester and Truck County of Wisconsin in the Madison area. An avid hunter, he enjoyed over 35 years of annual hunting trips to Montana. Dennis also liked watching NASCAR and attended races at numerous different tracks throughout the years. He loved traveling with family and friends, and cherished every summer they spent on Green Lake.

Dennis is survived by his wife, Susan of Markesan; children, Michael Jackowski of Green Lake and Kala Jackowski of Madison; sister, Linda (Randall) Brehmer of Markesan; brothers and sisters-in-law, nieces, nephews, other relatives and friends. He was preceded in death by his parents and other relatives.

Cornerstone Funeral & Cremation Services in Markesan is honored to be serving the family.