"Frank since the day I met you I had the utmost respect for you. Hardworking and REAL," Christina El Moussa captioned a photo of her with Miller.
"Always a pleasure to be around and always made me laugh. You fought your hardest!! You are so admired and respected by all who know you. God has a special place for you in Heaven. Love you and miss you. #RIP."
Miller was diagnosed this year with laryngeal cancer, which spread to his brain, E! News said.
El Moussa's estranged husband Tarek also paid tribute on social media to their longtime contractor.
The HGTV program follows the El Moussas as they buy, renovate and sell properties for profit.
"Good bye My dear friend Frank. I have always looked up to you and have respected you as a brother. You have touched not only myself and my family but thousands and thousands around the world. You have impacted so many lives with the fight inside your heart and soul," Tarek El Moussa posted on Instagram, along with his own photo with Miller.
"I've never met anyone like you nor will I ever. I just love you love you love you more than you know! I will NEVER forget you and I hope to one day be as strong as you. Now...don't slack!!!! I assume you are already working on remodeling heaven!!!!:):). Miss you buddy!"
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