General lighting has been widely used for office rooms in Japan. However, to reduce energy consumption it is important to use task and ambient lighting (TAL) systems in office rooms. It is known that TAL systems can minimize electric energy consumption without compromising lighting quality in office rooms To make TAL systems be used more widely in office rooms, it is important to take any measures to improve lighting quality, especially perceived room brightness in office rooms which employ TAL systems. We conducted two experiments in a real office room and 1/10-scale office model rooms. In the real office experiment, we employed a proposed TAL system that adopts suspended indirect luminaires as ambient lighting. This is because we hypothesized that the proposed TAL system could reduce gloomy non-lit areas by the indirect ambient lighting and therefore increase perceived room brightness. We measured the energy consumption of the office room and evaluated the quality of the working environment by using questionnaires. From the results, we found that the proposed TAL system with indirect ambient lighting helped reduce deep shadows and discomfort glare, and therefore improved its lighting quality. In addition, the TAL system with indirect ambient lighting reduced lighting energy by about 40% from conventional general lighting. In the additional laboratory experiment using 1/10-scale models, we compared the lighting quality of the TAL system using indirect ambient lighting with a TAL system using direct ambient lighting, a TAL system with dimmed ambient lighting, and a general lighting system. In this experiment, we confirmed the results of the real size field experiment and found the lighting quality of the TAL with indirect ambient lighting to be better than the other lighting systems. However, this study found the brightness uniformity of the TAL with indirect ambient lighting to be worse than the general lighting and TAL with direct ambient lighting systems. On the other hand, physical indexes such as luminance uniformity (minimum luminance over average luminance) and luminance variation coefficient (luminance standard variation over average luminance) showed better performances for the TAL system with indirect ambient lighting than for the other lighting systems. This implies that luminance modulations within a certain special frequency range may influence perceived brightness uniformity and therefore perceived room brightness. Further research is needed to investigate the mechanisms of how people evaluate uniformity of luminance distributions in lit office rooms.