The study investigated the influence of the business climate on the ethical decisions of Nigerian accountants; assessed the effect of organizational ethical value on their ethical reasoning and compared the ethical perceptions of accountants with professional qualifications with those without professional qualifications. It also evaluated the influence of the knowledge of tertiary accounting courses on the ethical predispositions of Nigerian accountants in training and finally examined the relationship between the demographic traits of age, gender, culture and religion and the ethical or unethical inclinations of Nigerian accountants. These were with a view to determining the factors that shape the ethics and financial practices of accountants in Nigeria. Primary data was utilized for the study. The population for the study comprised of 39,389 professionally qualified accountants registered with the Institute of Chartered Accountants of Nigeria (ICAN) and Association of National Accountants of Nigeria (ANAN), 19,600 first and final-year accounting students in 49 Universities in Nigeria offering accounting programmes as well as accounting practitioners without professional qualification. Judgemental dimensional sampling was used to select 850 accountants drawn from five major business cities in Nigeria and 370 first and final year accounting students from five Universities that offered accounting programme. Two sets of questionnaire were used to obtain data from respondents. The first questionnaire obtained information from the selected accountants on their ethical judgements to selected accounting ethics dilemma. The second questionnaire collected data from the selected accounting students to determine how the knowledge of accounting courses influenced their ethical predispositions. Data obtained were analysed using descriptive and inferential statistics such as T-test, Repeated Measures Anova, Mann-Witney U, Kruskal-Wallis, Chi-square and Multivariate Analysis. The results of the study revealed that the ethical decision of Nigerian accountants was significantly influenced by unethical practices in the business environment as well as by unethical organizational values. The mean ethical score which was 3.42 under a normal situation reduced to 1.94 under an unethical business environment (p<0.05) and to 2.53 under an unethical organizational environment (p<0.05). There was no statistically significant difference between the ethical responses of accountants with and without professional qualification (p=0.699); which provides evidence of the lack of the impact of professional accounting qualifications on accountants ethics and financial practices. The study also found that knowledge of accounting courses significantly decreases ethical predispositions of accounting students as the average mean score and mean rank of ethical perception for 100 level students was 3.89 and 223.08 while for 400 level students it was 3.26 and 130.66 (p<0.05). A statistically significant relationship was established between the demographic variables of age (p = 0.008), gender (p = 0.001), culture (p= 0.001), religion (p = 0.001) and the ethical or unethical inclination of Nigerian accountants. The study concluded that business environment and organizational ethics do affect the ethical decisions that Nigerian accountants make and that a significant relationship exist between the ethical predispositions of Nigerian accountants and the demographic factors of age, gender, religion and culture.