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. All of her comics were printed in Japan in digests of comic book form; 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 2010.
Selected comics were translated into English, under the title The Wonderful World of Sazae-san.
Hasegawa Machiko remained single all her life. All her comic books were published by Shimai-sha which her sister ran. In 1985, Machiko opened her own art gallery and exhibited her original works. Even though she was sometimes hospitalized with a stomach ailment, she continued to draw the comic strip. After she died, she was awarded a posthumous prize by the Prime Minister. "Sazae- san" hasn't declined in popularity even after her death, on the contrary, it is still loved and read by many people.