The study investigated behavioural patterns and factors responsible for students attention deficit hyperactivity disorder (ADHD) in Ikwerre Local Government Area (LGA) of Rivers State (R/S), Nigeria: An implication for instructional designer. The researchers espoused descriptive research design. The study had three (3) purpose of study, three (3) research questions in addition to two (2) hypothesis. The population encompassed of 13,950 senior secondary school (SSS) students in the thirteen (13) public SSSs in the LGA under study. Taro Yamen’s formula for determination of sample size stood espoused to acquire a target population of 400 as sample size with the assistance of the stratified random sampling technique (SRST). The SNAPIV ADHD rating scale as well as DBDRS established by Swansen Nolan and Pelham stood espoused as research instrument retitled as characteristics behavior as well as factors accountable for attention deficit hyperactivity disorder questionnaire (CBFRADHDQ). The instrument remained validated by specialists in the area of measurement and evaluation. The reliability coefficient value of 0.65 to 0.92 was established through Pearson’s Product Moment Correlation co-efficient (PPMCC). The data was analyzed through mean plus standard deviation for the research questions then t-test for the hypothesis. The study found that the factors accountable for ADHD ranged from nature to nurture, genetic/neurological factors and environmental factors amid others. It was also confirmed that there is a significant difference in the behavioral patterns of ADHD based on school location and there was no significant difference in the factors accountable for ADHD based on sex. The following recommendations were made amid others. Instructional designers should be engaged in instructional resource centres in rual and urban schools to identify appropriate learning approaches and design for differentiated instruction for ADHD to benefit maximally from teaching-process. School health programmes should be conducted from time to time to offer veritable avenue for the identification of ADHD.