The application of the soundscape approach is becoming increasingly prevalent in the evaluation of indoor acoustic environments, including office environments. However, the formalisation and standardisation of soundscape assessment methods for offices remain in the early stages, highlighting the need for further development. This systematic review explores the methods and factors involved in soundscape assessments within office environments, which are intended to contribute to creating or improving comprehensive and widely accepted protocols. This review includes 41 studies, revealing that questionnaires (n = 36) are the most commonly used subjective tools, occasionally supplemented by interviews (n = 1). Some studies employ a combination of questionnaire and interview (n = 2), questionnaire and discussion (n = 1), or all three methods—questionnaire, interview, and discussion (n = 1). Meanwhile, direct acoustic measurements (n = 28) and cognitive tasks (n = 14) are often employed for objective evaluations. Additionally, the review categorises factors involved in objective and subjective soundscape assessments into acoustic and non-acoustic elements. It also identifies tools frequently used to assess the correlation between soundscapes and physical and psychological well-being. Collectively, this review underscores the critical factors for comprehensive soundscape assessments in office environments.