The Church of Scientology is not Christian by any standard definition of Christianity. It does not affirm the existence of the Christian God, the Trinity, Jesus Christ as Lord and Savior, salvation by grace through faith, or the authority of Scripture. It is a wholly different religion — rooted in L. Ron Hubbard's science fiction worldview — that explicitly meets the definition of a cult on both theological and sociological criteria. 2/100 Avoid.
The Church of Scientology was founded in 1954 by L. Ron Hubbard, a science fiction writer who developed his ideas initially in the 1950 book Dianetics. Scientology's core beliefs: humans are immortal spiritual beings (Thetans) whose true potential is suppressed by traumatic memories (engrams) stored in the "reactive mind"; through a process called "auditing" (guided questioning using an E-meter device), Thetans can be "cleared" of engrams; advanced levels of Scientology (OT levels, kept secret from lower members) teach that 75 million years ago a galactic ruler named Xenu brought billions of people to Earth and killed them with hydrogen bombs, and that their spirits (Body Thetans) now cling to humans causing psychological problems.
This theology has nothing in common with Christianity. There is no personal God in Scientology, no Jesus as Lord or Savior, no Trinity, no sin in the biblical sense, no grace, no Scripture. The comparison point is not "how different is their Christianity" but "this is a completely different religion with no meaningful Christianity in it."
Scientology meets both the theological and sociological definitions of a cult comprehensively. Theologically: it denies every essential Christian doctrine while claiming to be compatible with Christianity (Hubbard claimed Scientology was compatible with any religion). Sociologically: Scientology has been classified as a cult and/or dangerous organization by courts in multiple countries, by former members' accounts, and by the application of every standard cult-behavior checklist.
The FTC and law enforcement agencies in multiple countries have investigated Scientology for fraud. Former members' accounts describe the full range of cult behaviors: financial exploitation at scale, shunning ("disconnection") of family members who leave, harassment of critics, and the Secret Police (Office of Special Affairs) that Hubbard designed to destroy the enemies of Scientology.
For Christians: there is no meaningful sense in which a Christian should consider participating in Scientology or its related organizations. The beliefs are incompatible with Christianity at every level. See our cult warning signs guide, our guide on Is Mormonism Christian?, and our Church Assessment hub.