Discretion is the root source of administrative agency power and influence, but exercising discretion often requires agencies to undergo costly and time-consuming pre-decision assessment programs, such as under the Endangered Species Act (ESA) and National Environmental Policy Act (NEPA). Many federal agencies thus have argued strenuously, and counter-intuitively, that they do not have discretion over particular actions so as to avoid such pre-decision requirements. Interest group litigation challenging such agency moves has led to a new wave of jurisprudence exploring the dimensions of agency discretion. The emerging body of case law provides one of the most robust, focused judicial examinations of the nature and scope of agency discretion available in modern administrative law, but agency discretion aversion and the concerns it raises have gone largely unaddressed in legal scholarship. And yet the discretion aversion syndrome is primed only to expand as climate change implicates a broadening span of agency programs as having environmental impacts. This Article is the first to comprehensively describe and assess the ESA/NEPA discretion aversion trend to extract what it has to say not only about agencies, courts, and statutes, but also about agency discretion in general. Part I describes the origins and features of the ESA and NEPA assessment programs leading to agency discretion aversion. Part II identifies the strategies agencies use to escape the ESA and NEPA assessment programs by disclaiming discretion. Part III probes institutional concerns for agencies, courts, and the statutes that arise from the discretion aversion syndrome, including agency gaming behavior, judicial conflicts regarding when nondiscretion exists, and compromised statutory purposes. Before turning to solutions, Part IV steps back to assess what questions the ESA and NEPA nondiscretion case law raises for the conceptualization of agency discretion writ large, identifying discretion’s “negative space” as the source of tension between agencies and courts. Part V then circles back to reexamine the ESA and NEPA nondiscretion doctrines, evaluating alternative measures to deflate agencies’ discretion aversion impulse while promoting the statutes’ purposes. We conclude that the most effective reform will be to eliminate discretion as the litmus test for the ESA and NEPA, replacing it with criteria more responsive to the statutes’ twin purposes of improving agency decisions and providing information to other political institutions and the public.