She started her own comic strip, Sazae-san, in 1946. It reached national circulation via the Asahi Shimbun in 1949, and ran daily until Hasegawa decided to retire in February 1974. She also created the comic strip Granny Mischief. All of her comics were printed in Japan in digest comics; by the mid-1990s, Hasegawa's estate had sold over 60 million copies in Japan alone.
Her comic strip was turned into a dramatic radio series in 1955 and a weekly animated series in 1969, which is still running as of 2013.
Selected comics were translated into English, under the title The Wonderful World of Sazae-san.