Introduction: Improving the quality of clinical education requires a continuous review of the status quo, recognition of strengths and weaknesses, as well as correction of these weaknesses. Besides, the experiences of ICU students can be useful in removing such weaknesses. The objective of the present study was to investigate the personal experiences of nursing students about the characteristics of an effective clinical instructor and to explain the concept of “effective instructor” in clinical education. Methods: This qualitative study was conducted based on van Manen’s phenomenology. Using purposive sampling, 12 nursing students working in the intensive care unit of Qazvin University of Medical Sciences were selected and studied. The data were collected by conducting in-depth semi-structured interviews. All interviews were recorded and then the related codes and themes were extracted using van Manen’s analysis method. The validity and robustness of the study were obtained through attention to the four axes of validity, trustworthiness, reliability, and generalizability. Results: The transcripts of the interviews were analyzed and conceptual codes were extracted. After analyzing the data, 12 categories, 51 subcategories, and 5 themes were extracted. The extracted themes included scientific and practical competence, communicator and clinical coordinator, professional behavior guide, theoretical-clinical mediator, and fair evaluator. Conclusion: Based on the findings, the participants in this study emphasized the key role of the instructor in creating a suitable context for professionalization. They acknowledged that an instructor with good personality traits, speaking skills, management, appropriate clinical competencies, effective professional communication, and a realistic evaluation can train qualified students to work in the country’s healthcare system.