The convergence between telecommunication, broadcasting multimedia and related technologies commonly known as Information and Communication Technologies (ICT), promises a fundamental change in educational management. ICT could be the missing tool in improving efficiency of private secondary schools to cope with rapidly changing world to effectively meet management tasks combined with flexibility in learning and administrative activities essential in enhancing efficiency in educational institutions. Little evidence explains effect of ICT in private secondary schools management across the globe. The study investigated effects of ICT in management in private secondary schools in Nairobi. A survey design was adopted with target population of 140 private schools and information was sourced from 40 principals, who were randomly sampled. The study found that the adoption of ICT is high in private schools irrespective of curriculum offered. The use of ICT with schools having installed current hardware and software required for implementation of ICT strategy in management. Findings revealed that use of ICT is more in schools with higher enrollment and having both day and boarding components. Uses of ICT enabled institutions achieve improvements in financial, administrative and instruction management. In financial management 62.5% of schools had automated accounts, 71.9% payroll and 53.1% budgeting operations. In administrative management 68.75% automated stores, 56.25% students' records and 62.50% staff records. In instructional management 53.10% automated timetabling, 84.30% examinations and 76.90% students' progress reports. The study recommends regular training of administrators and staff on emerging technologies in school management, deliberate budgetary allocation to procure hardware and software to support ICT in management and government policy to implement ICT in management at all tiers of the economy.