The medals were an heirloom Bill Chidlow left to his eldest son Leon after he died in 2013.
Leon's sister, Jocelyn Doak, said the medals, engraved with her father's name, had been kept at her brother's Dunsborough home for two years before she wore them at an Anzac Day commemoration this year.
Ms Doak said she borrowed the medals to wear to the Albany commemoration in honour of her father and now felt guilty for doing so.
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READ NOW"We met as a family, the four siblings, on April 26 at Botanica Bar and Bistro for lunch, and I handed the medals over to my brother Leon and that was the last time we saw them," she said.
"We met at Botanica because dad used to meet there with his brothers for his birthday and we wanted to come here to have a celebration in his honour."
Mr Chidlow served in the 28th Battalion and was a quiet man who kept the traumatic memories of war to himself.
Ms Doak said after lunch at Botanica her brother went to Spudshed Innaloo and back to his daughter's home in Edgewater. She hopes someone may have found the medals or seen them.
The Kingsley resident said it was a horrible feeling not knowing where the medals were and hoped that they had not been tossed in the rubbish.
Anyone with information about the medals should contact the Returned and Services League or police.