Museum and Library Services Act of 2018 This bill amends and reauthorizes through FY2025 the Museum and Library Services Act and provides funding for library services and technology through FY2025. (Sec. 8) The bill expands the definitions of "library" and "museum" to include a tribal library or museum and expands the services museums are authorized to provide. (Sec. 19) The Institute of Museum and Library Services, under the 21st Century Museum Professional Program established by this bill, may enter into arrangements with museum, museum consortia and associations, institutions of higher education, and other entities for projects to increase the number of students from diverse and underrepresented backgrounds enrolled in graduate and undergraduate museum-related programs; recruit future museum professionals from such backgrounds; develop new or enhance current professional development and retention programs for museum professionals and the museum workforce; and support and conduct research, needs assessments, pilot programs, and evaluation of education and professional development programs to recruit, prepare, educate, and retain the next generation of museum professionals.