Succession planning (SP) and employee retention (ER) are mutually reinforcing. Meaning ineffective succession planning leads to turnover, and that would, in turn, make the succession plan ineffective. Hence the big challenge is to find how SP affects ER. For this, we proposed a model explaining the mediation effect of various factors on SP-ER nexus. We hypothesize that proper Succession planning produces a positive effect on Performance Goal Orientation, Supervisor Support, Working Environment, Rewards, Work-life Policies, Career Development, and Job Security. And these factors, in turn, lead to employee retention. We further assumed that the ER would lead to Organizational Effectiveness. To establish its empirical validity, we conducted a survey using a close-ended questionnaire. Data was gathered from 300 respondents who are serving in the middle and lower level of management in the private organizations in Pakistan. Data analysis was done through the descriptive statistics, partial least square (PLS), and Structural Equation Modeling (SEM) with the help of SmartPLS3. The findings indicated that effective succession planning practices had a meaningful, favorable connection with employee retention and out of seven mediators, only three mediators i.e. job security, rewards, and supervisor support significantly mediated the association between effective succession planning practices and employee retention. Succession planning also seems to significantly affect the working environment, work-life policies, and career development. Results also exhibited that there’s an insignificant link between effective succession planning practices and organizational effectiveness and also there is no positive relationship between employee retention and organizational effectiveness.