In viscosity measurement, temperature control is very important. In this study, the effects of temperature distribution on vibrational viscometers are investigated. Vibrational viscometers are preferred over other types of viscometers owing to their low cost, easy to use and efficacious continuous viscosity measurement capability. The study was conducted in two parts. In the first part, the challenge of unequal temperature distribution in vibrational viscometers was analyzed. The heat generated by a heater during continuous viscosity measurement disperses every part of a sample fluid and influences the fluid’s viscosity. Therefore, the sample fluid may have inhomogeneous viscosity values because temperature distribution cannot be equal at every point in a fluid. This experiment is repeated several times with different temperature gradients for gaining a better understanding about the effect of unequal temperature distribution on fluid viscosity. Experimental outcomes show that under some conditions, viscosity measurement errors could reach 27.9%. This finding has been verified by mathematical calculations. In the second part of the research, for solving the unequal temperature distribution problem, the use of a magnetic stirrer for mixing up the fluid throughout the viscosity measurement with the aim of achieving homogenous temperature distribution is proposed.