To measure the success of an influencer marketing campaign, track key metrics such as engagement rates (likes, comments, shares), website traffic, and conversions directly tied to the campaign. Use tracking links or discount codes to attribute sales. Analyze social media reach and follower growth, and monitor brand sentiment through comments and mentions. Evaluate return on investment (ROI) by comparing campaign costs with generated revenue. By analyzing these data points, you can assess the overall impact and effectiveness of your influencer marketing efforts.