Aggression and violence (A/V) in mental health care are all too frequent occurrences; they produce a wide range of deleterious impacts on the individual client, staff, organizations, and the broader community. A/V is a multifaceted and highly-complex problem, and is associated empirically with a wide range of phenomena. However, most attempts to reduce A/V in mental health care have invariably focused on one or two aspects of the problem at the expense of a more comprehensive, systemic approach; these have produced inconclusive results. As a result, this two-part paper seeks to: (i) recognize the wide range of phenomena that have been found to have an association with A/V in mental health care; (ii) synthesize these propositions according to fit or congruence into a systemic model of A/V; (iii) explore empirical evidence pertaining to these propositions; and (iv) begin to consider the application of this model to better inform our individual and/or organizational responses to A/V in mental health care. The paper advances a systemic model of these phenomena comprised of four thematic categories, with Part 1 of this paper focusing on the first two categories: environmental and intrapersonal (client-related) phenomena.