Very little is known about the architectural firms in Nigeria. The study thus explored the characteristics of architectural firms in Nigeria empirically using the systems approach to the study of organizations. The study investigated the organizational profiles, cultures, strategies and structures of the architectural firms. The tasks and information technology characteristics of the architectural firms as well as the external influences on the firms were also investigated, culminating in the investigation of the types of architectural firms that existed in Nigeria.This study thus took an approach which was exploratory and descriptive. Therefore, the research was mainly inductive. The architectural practice was studied as a professional organization and the architectural firms were studied holistically, taking the systems approach. The sample size was derived from the list of architectural firms registered by Architects Registration Council of Nigeria (ARCON, 2006). The purposive and random sampling methods were employed. The survey and qualitative methods were used, with the firm as the unit of analysis. The survey instrument was the structured questionnaire, while the qualitative instrument was the interview schedule. The ninety-two (92) questionnaires collected were analyzed using frequencies, cross tabulations, the chi-square test, principal component analysis, the coefficient of correlation (Pearsonâ€™s product-moment correlation coefficient), Multiple Analysis of Variance, (MANOVA), discriminant analysis, regression analysis and cluster analysis. The data from the interview were analyzed using content analysis. The five types of firms identified by the study included male-dominated firms, amorphous firms, conventional firms, stable/ traditional firms and versatile firms. The most important causes of differences between the types of architectural firms in Nigeria were level of specialization of activities, and varieties of services offered, which accounted for more than half of the differences between the firms. Most of the architectural firms sampled in Nigeria were found to be more than ten (10) years old, small sized, and owned by a sole principal. They had the culture of innovation, but not the culture of aggression in the pursuit of business opportunities or concern for profit. The study found that most of the clients of the architectural firms were private individuals in Nigeria and most of their projects were residential projects. Most of the clients of the architectural firms were sourced through personal contact and the projects most of the firms carried out were those that they were able to obtain commissions for. Most of the firms were engaged in projects which used the design and build method and these firms were found to have more residential projects. Also participation in design and build method appeared to be a survival strategy as the firms that had existed for more than 15 years did not participate in projects which used this method. The firms mostly used competence in design, followed by AUTOCAD and information technology literacy as criteria for the selection of staff. Findings of the study indicated that information technology facilities were highly available in most of the firms, and the internet was mostly used for sourcing information. The results also suggest that the internet was used as a tool for centralization. The study further found that the external influences on most of the architectural firms were not so strong and the greatest influences were those exerted by clients, advances in information technology and the national economy. The characteristics of the firms most affected by these external influences were the staff management culture of the firms, the strategic goals of the firms and the qualification and experience of the principal. The study concluded that architectural firms need to take advantage of the opportunities provided by information technology to operate on a global level. There is a need for architectural schools in Nigeria to fully integrate internship into the study of architecture as well as train students extensively in construction methods to meet the demands of architectural firms. The study further concluded that there is a need for the business training of architects as this was a factor responsible for the success of architectural firms. The systems approach to the study of architectural firms had been useful and practical. More studies are required, using the systems approach, on peculiarities of architectural firms and their management strategies.