Catherine Shaw, 23, from Witney, Oxfordshire, has been travelling since September past year and was reported missing on March 5.
Her parents have made a video appeal through the Lucie Blackman Trust, which helps families of those missing overseas.
She had been staying in the Lake Atitlan area of the central American country and was last seen by a friend the previous night.
Ms Shaw has been travelling since September and has been to Mexico and California.
The organisation, which provides support for the families of people who go missing while overseas, said the woman was travelling with another female and was "hitch hiking".
Rescuers have called on travellers who could have been mistaken for Miss Shaw to come forward so they can be ruled out.
According to The Telegraph, she was last seen leaving the Eco Hotel in Mayachik, shortly before 5.30am on Tuesday, carrying a stray puppy.
"So this is unusual behavior which gives us great concern for her safety".
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In a statement, they said: "She has always been really good about keeping in touch and informing us of her whereabouts". Lake Atitlan is surrounded by mountains and volcanoes, but San Pedro itself is packed with a strip of lively bars known as the "Gringo Trail".
He added: "Your friends, your family are all really anxious about you, please come home sweetheart".
"If anybody has any information, at all, please contact us, the Lucie Blackman Trust, or the police", added her father.
Guatemalan police, local residents and British people in the country helped search for Shaw near the area where the puppy was found over the weekend.
A spokesperson for the hotel has confirmed her belongings has been left behind.
In a Facebook post she said that Catherine seemed "really sad" before disappearing and that they played music together late on Monday before she went to bed.
Shaw's mother urged her daughter to get in touch with friends and family if she is alive.