Winfrey, 62, took to social media to pay tribute to the television icon, and shared a sweet flashback photo of a previous on-screen meeting between the pair.
She tweeted, "Even now looking at this picture I want to cry. I still can't believe Mary Tyler Moore touched my face. Will love her 4 ever."
And in a separate message posted on Instagram, she said: "Dear Mary, You already know how you majorly influenced my life and career. I respected and admired your business acumen, your passion and compassion for all life, and most importantly, the values espoused through your storytelling.
The small screen superstar died on Wednesday surrounded by family members who flocked to say their goodbyes at a Connecticut hospital.
Her publicist, Mara Buxbaum, said in a statement, "Today, beloved icon, Mary Tyler Moore, passed away at the age of 80 in the company of friends and her loving husband of over 33 years, Dr S Robert Levine.
"A groundbreaking actress, producer, and passionate advocate for the Juvenile Diabetes Research Foundation, Mary will be remembered as a fearless visionary who turned the world on with her smile.