Abstract Objectives The aim of this study was to translate and validate the condition-specific Oral Health Impact Profile (OHIP) in the Croatian cultural context and assess the impact of periodontal diseases and nonsurgical periodontal therapy on quality of life (QoL). Materials and Methods A cross-sectional study was carried out on 150 individuals: 50 periodontally healthy, 50 with gingivitis, and 50 with periodontitis who self-administrated the OHIP. The participants' age ranged between 18 and 71 years, with the median age of 45 (34–57) years. Forty-seven percent of the participants were females. The validity and reliability of the Croatian OHIP version were tested. The impact of gingivitis and periodontitis on QoL was assessed. Changes in QoL induced by nonsurgical periodontal therapy in 20 patients with periodontitis were analyzed. Statistical Analysis Categorical data were presented by absolute and relative frequencies. The normality of the distribution of continuous variables was tested by the Shapiro–Wilk test. Continuous data were described by the median and the limits of the interquartile range (IQR). Differences in continuous variables between two independent groups were tested with the Mann–Whitney U test, and between three groups with the Kruskal–Wallis test (post hoc Conover). The Wilcoxon signed-rank test was used to examine the differences in the total score before and after therapy. All p values were two-sided. The level of significance was set at alpha of 0.05. Results The analysis detected a single-factor structure that explained for the 56.9% of the variance. Cronbach's alpha value was 0.937, which indicated an excellent internal consistency. Overall OHIP score reported a strong correlation with the subjective estimate of periodontal problems (Rho = 0.92; p