Despite a downwards trend in smoking prevalence, smoking remains the UK's biggest preventable cause of premature mortality. Specialist stop smoking support programmes provided by the NHS have helped to reduce smoking prevalence and whilst there has been a vast amount of research investigating the most effective behavioural and pharmacological support models, little is known about the impact of smoking cessation advisor's smoking status and clinical effectiveness on quit rates. This study aimed to identify factors that contribute to NHS stop smoking advisor performance using a quantitative cross-sectional design via an online survey that was completed by 159 participants in 24 London boroughs. Multiple regression analyses revealed that level of training, years practiced, level of advisor education, number of patients supported in a given year, and smoking status had no significant impact on NHS stop smoking advisor quit rate in this sample. However, the model revealed that proportion of time spent delivering smoking cessation support was significantly associated with quit rate. It is imperative that this finding is considered when recruiting, commissioning, and training new smoking cessation advisors or provider organisations.