The study examined the determinants of modified audit opinion of listed non-financial firms
in Nigeria. The objective of the study was to investigate whether audit firm size has
significant effect on modified auditor opinion in non-financial firms in Nigeria. The
secondary source of data collection was adopted in the study where the purposive sampling
technique was used to select a sample size of ten (10) non-financial firms in Nigeria for the
study. Least Square regression analysis was used in this study and the findings revealed that
audit firm size has significant effect on modified auditor opinions in non-financial firms in
Nigeria. The study concluded that the size of the board will influence the likelihood of a firm
receiving modified audit opinion and firms with large boards were less likely to receive
modified opinion due monitoring effectiveness of large boards. Finally, it was recommended
that the size of the audit board should be properly partitioned to ensure a balanced opinion
and adequate representation of the financial status of the firm.