The effect of ultrasound in combination of heat on the extraction yield and technological properties of chia seed mucilage was investigated. Chia seeds were mixed with distilled water at a seed-to-water ratio of 1:30. The dispersion was adjusted to pH 9 and treated either with heat extraction by water bath or with heat/ultrasound extraction by probe-type sonication at 50 °C and 80 °C for 30 and 60 min. The yield and technological properties of mucilage samples were evaluated. The heat/ultrasound extraction gave a greater yield of mucilage (6.92−10.52%) as compared to the heat extraction (1.03−1.86%). Images obtained from Scanning Electron Microscope (SEM) have shown that during heat/ultrasound extraction, the amount of mucilage fibers on the surface of chia seed decreased with the increased extraction time. Thus, the yield of mucilage prepared with heat/ultrasound extraction for 60 min was significantly higher than that of mucilage extracted for 30 min. However, the difference between the seed samples treated with heat/ultrasound extraction at different temperatures was not apparent. The mucilage prepared with heat/ultrasound extraction at 50 °C for 60 min had the best technological properties. The amount of protein in the heat/ultrasound extracted mucilage diversified its technological property. Moreover, the mixture of mucilage and whey protein isolate had better miscibility. This study confirms the great potential of application of ultrasound in combination with heat in the extraction of chia seed mucilage.