Table 2. Characteristics of included studies.

Study	Design	Population	Setting	Onboarding program/practice	Comparison	Outcomes
1	RCT	New nurses. BSc. No prior internship. n: T 31; E 16; C 15 Age (M): 22.32 Gender F: 100%	One hospital, different work unit Taiwan Year 2014.	Situated and simulated nursing activities. Format: Face-to-face support sessions. Dose: Six sessions of 1–2 hours. Frequency: Missing. Duration: Three months. Content: Instructor-led situated and simulated commonly occurring clinical situations focusing on recognizing signs and symptoms of diseases, understanding medication regimens, interpret laboratory data, and recognize communication difficulties between the nurses and the patients. Components: Instructor guided participation, questions, and reflection on learning outcomes.	Self-oriented learning. No details about content, format, dose, or duration.	Competence. Post-intervention.
2	RCT	New nurses. BSc. n: T 239; E 130; C 109 Age (M): 27.5 Gender F: 85%	One hospital, different work units. Sweden Year 2016–2017.	Intervention to increase engagement in proactive behaviors. Format: Group sessions with 10 new nurses and one group leader. Dose: Nine hours plus homework assignments Frequency: Three sessions of 3 hours every other week. Duration: Four weeks. Content: Theory about organizational socialization and proactive behaviors, theory about stress and recovery, group discussions, individual pen-and-paper exercises. Components: Behavior change techniques approach behaviors, systematic exposure, and action planning, homework assignments.	Didactic sessions and skills training. Format: Didactic sessions and skills training. Dose: Nine hours. Frequency: Three sessions (3 hours each) every other week. Duration: Four weeks. Content: Theory and practice on patient care (e.g., nutrition, wound treatment), communication skills, team management, and the role, rights, and responsibilities of nurses.	Role clarity Task mastery Social acceptance Post-intervention.
3	Observational	New professionals (accountancy, auditing, banking, software, chemical and manufacturing industries) n: T 244 Age (M): 23.6 Gender F: 51%	Unspecified professional settings	On-the-job training (no intervention)	n.a	Role clarity Role conflict Role orientation Four-five months into profession.
4	Between-groups comparison	New nurses. Different degrees (prelicensure diploma, associate-degree, BSc, or MSc) n: T 763; E 577; C 186 Age (M): 28 Gender F: 91%	Multiple hospitals, different work units. USA Year 2011	NCSBN’s transition-to-practice program. Format: Online course plus preceptorship. Dose: ≥ 20 hours per month for the first 6 months. Frequency: Not specified. Duration: 12 months. Content: Online modules covered the topics patient-centered care, communication and teamwork, evidence-based practice, quality improvement, and informatics. Components: An institution-based orientation program, preceptor for the first six months of practice, educational online modules for the first six months, safety and clinical reasoning threaded throughout the modules, institutional support during the second six months of the program, feedback and reflection.	Original transition-to-practice programs of the health facilities in the control group. No details about content, format, dose, or duration.	Competence (overall) Patient-centred care Evidence-based practice Use of technology Communication and teamwork Post-intervention, 9 and 12-months follow-up.
5	Between-groups comparison	New nurses. Degree not specified. n: T 332; E 234; C 85 Age (M): 23.5 Gender F: 83.9%	Different hospitals, different work units. Vietnam. Year 2019–2020.	Clinical training program. Format: Clinical training, preceptorship, classroom-based activities Dose: 1520 units. Frequency: Not reported. Duration: Nine months. Content: Clinical training (on-the-job training = ward-based practices involving patients; off-the-job training = classroom-based lectures, discussions, group works, experiments, and practices), preceptor; and systematic management.	Original training program of the health facilities in the control group. No details about content, format, dose, or duration.	Competence (total). Post-intervention.

Note: Study 1 = Chen et al. (2017); Study 2 = Frögéli et al. (2020); Study 3 = Kowtha (2011); Study 4 = Spector et al. (2015); Study 5 = Horii et al. (2021); n = number of participants; T = total number of participants; E = Experimental group; C = Control group; M = mean; n.a = not applicable.