Mark Sean O'Donnell

Mark Sean O'Donnell, 69, of Encinitas, CA passed away peacefully surrounded by his family on Wednesday, February 25, 2026. He leaves his wife of 43 years, Patricia A. (Palmer) O'Donnell, his son, Patrick B. O'Donnell and his wife Kristy, of Encinitas, CA and his daughter Megan P. (O'Donnell) Faulstich and her husband Brian of Carlsbad, CA. His three sisters, Deborah, (O'Donnell) Rocheleau and her husband, Richard Rocheleau of Port St Lucie, Florida, Deirdra (O'Donnell) Rogers and her husband Glenn Rogers of Port St Lucie Florida and Ellyn (O'Donnell) Carrington and her husband Daryl Carrington of Vero Beach, Florida and his brother Edward F. O'Donnell and his wife Jayne of Avon, CT. 

He leaves his seven grandchildren Teagan, Kennedy, Madison, Rian, Blake, Tatum, and Jack and his several nieces and nephews. He was predeceased by his sister, Dorothy (O'Donnell) Bessette and brother Michael P. O'Donnell.

He was Born in Waterbury, CT the son of the late Edward Francis O'Donnell and Dorothy (Breheny) O'Donnell. He attended Holy Cross High School in Waterbury. Mark received his bachelor's degree from the University of Connecticut and MBA from the University of New Haven, CT

Mark built a distinguished and successful career in the Life Science industry. Over the years, he held leadership position at PerkinElmer, Applied Biosystems, Life Technologies, and Thermo Fisher Scientific. His intelligence, work ethic, and integrity earned him deep respect from colleagues and friends alike.

Above all else, Mark was a devoted husband and loving father. He was married to his beloved wife, Patricia Ann O'Donnell, a partnership built on love, loyalty, and unwavering support. He was the proud father of Patrick O'Donnell and Megan Faulstich, and nothing brought him greater joy than time spent with his children and grandchildren. 

Mark was a passionate Boston sports fan, proudly cheering on his teams through every season. He loved playing softball, and golf, relaxing at the beach with his family and especially playing with his grandchildren. His presence was steady, warm, and full of humor. Those who knew him will forever remember his optimistic spirit and his favorite saying: "Every day is a good day." 

Mark leaves behind a legacy of love, strength, and dedication to his family, his profession and to living life with gratitude. He will be deeply missed and forever remembered. 

His funeral mass will be held on Wednesday, April 8th, 2026, at Saint John the Evangelist Catholic Church in Encinitas, CA

In lieu of flowers, donations may be made to:

Alzheimer's San Diego 3635 Ruffin Rd, STE 300, San Diego, CA 92123