Bestortha Brahaj, aged 22, and her three-year-old daughter Elia were last seen yesterday evening at their home in Shirecliffe.
A South Yorkshire Police spokeswoman said: "We are growing increasingly concerned for the females’ welfare.
"Bestortha is a white female with a tanned complexion around 5ft 5ins tall, slender build with shoulder length dyed red hair. Last seen to be wearing a brown hooded coat, black trousers, white trainers and carrying a black shoulder bag.
"Elia was wearing a white long sleeved top, red scarf with a matching red and white 'Minnie Mouse' polka dot hat, dark trousers and white trainers.
"Do you know where Bestortha & Elia are?"
Contact police on 101, quoting incident number 1193 of 20th April 2017.