This study examined the Impact of Online Advertising on Customers Satisfaction of E-tailing Firms in Nigeria. A survey research design was adopted. The source of data used in this study was mainly primary data from the issuance of questionnaire and secondary data from the review of relevant literature bothering on both variables which formed the basis for the argument. Out of a total of three hundred and eighty four (384) copies of questionnaire distributed, two hundred and eighty five (285) copies was used for analysis and analyzed using Spearman’s Rank Order Correlation Coefficient with the help of Statistical Package for Social Sciences (SPSS). The findings of the study reveal amongst others that there is a positive and strong relationship between online advertising and customers’ satisfaction;and online advertising significantly affects customer satisfaction. The study concludes that online advertising influenced satisfaction of the customers to a strong extent. However, online advertising is a key determinant of customer satisfaction as it is considered as a point of interaction between customers and the company from which they buy their products. A heuristic model was proposed to show our contribution to knowledge that the relationship between e-mail marketing and measures of customer satisfaction is very strong and is moderate on all other tested hypotheses. And the study recommends that advertising managers of e-tailing firms must develop and formulate e-mail marketing programs that will satisfy the needs of consumers and advert should be placed on stations and places where consumers can easily identify with them and make a purchase. Suggestions for further studies were outlined.