Marketing is a core management function for any business, but smaller tourism businesses seem to underestimate the value of effective marketing and handle marketing in a more informal and unstructured manner. This can decrease their effectiveness in attracting tourists and influence the success of their businesses. The purpose of this study was to investigate the relationship between marketing effectiveness and the application of the marketing mix by guesthouses in the Vaal Region. This was done using a structured questionnaire for which 451 were completed and used in the statistical analysis. Descriptive (frequency tables, factor analyses) and inferential (Spearman rankorder correlations) statistics were performed to determine the relationship in question. The results revealed five independent marketing mix factors with high levels of internal consistency, namely product (most important factor), place, price, promotion: advertising and promotion: direct contact. In the case of marketing effectiveness, two factors were identified, namely quality control (most important factor) and quantity control. Significant positive relationships were found between the adapted marketing mix and marketing effectiveness factors, with the strongest correlations found between price and quantity control as well as quality control. Smaller businesses such as guesthouses should take the adapted marketing mix factors seriously if they wish to be successful in their business and, if they lack skills and knowledge in this regard, it is worthwhile to improve their current knowledge or ask a marketing expert to assist in this process. It was clear that smaller businesses such as guesthouses should not underestimate the value of well-planned marketing efforts that are based on the marketing mix.