Conditional sentences are difficult for EFL students to understand because of their complexity in both form and function. By analyzing the performances and opinions among EFL learners, the pedagogical contribution may be beneficial for both EFL students and teachers. The use, errors, and perceptions of Thai EFL students regarding conditional sentences were explored in this study. Instruments of the study included a chapter test, writing assignments, and an online survey. Data were analyzied by means of Google Form and AntConc software. The results of the test revealed that the participants performed best on the zero conditional type, while the first conditionals were used the most in their writing. Findings of the error analysis revealed that some difficulties in the use of tense were widely occurring such as using present progressive instead of present simple tense on the if-clause for zero type. Following that, the participants believed that the second conditionals were the most difficult, while the zero conditionals were the easiest.