This quantitative research aimed 1) to study the level of perception of product quality, brand image, brand equity, and brand loyalty, and real estate agents and 2) to study causal influences on brand loyalty among real estate agents in the second-hand real estate market in Bangkok Metropolitan. The sample included 400 service users or participants in the decision to use real estate agent in the second-hand real estate market in Bangkok and Metropolitan during the first and second quarters in 2022. The statistics used included percentage, mean, standard deviation, and analysis of structural equation modeling. The analysis results revealed that most participants were female (62.5 percent), aged 31-40 years old (59.3 percent), business owners (37.5 percent), with bachelor's degrees (59.5 percent) and income of 30,001-45,000 baht (33.5%) and also found that the level of perceived product quality, brand image, brand equity, and brand loyalty overall was at a high level. The analysis of the structural equation modeling revealed that the model was fit with the empirical data as follows:  2 = 131.769, df=108,  2 / df =1.220, p-Value = 0.060, SRMR= 0.021, RMSEA= 0.023, GFI= 0.967, CFI= 0.996, and NFI= 0.977. Perceived product quality influenced brand image, brand equity, and brand loyalty. Perceived product quality indirectly influenced brand image and brand loyalty. To sum up, service users perceived product quality, brand image, and brand equity but brand equity slightly affected the decision to use real estate agents in the second-hand real estate market