Human Resources Generalist

About the job

Why Castelion, Why Now

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability.

This is a rare opportunity to join at an early stage, where you'll have significant ownership, collaborate with exceptional teammates, and make a direct, measurable impact on our mission and the future of the company - regardless of your function.

Role Overview:

The Human Resources Generalist will play an important role in supporting the core people operations that enable our teams to do their best work—on the ground and beyond.

You’ll support the day-to-day execution of essential HR processes across onboarding, payroll, benefits administration, and people analytics. Partnering with HR and cross-functional teams, you’ll help maintain accurate, compliant, and employee-centric processes while contributing to operational improvements that support our rapidly growing workforce.

Responsibilities & Outcomes:

Payroll Support

• Support accurate and timely payroll processing, ensuring employee pay information is complete and up to date.

• Support and resolve routine payroll discrepancies and employee inquiries in a timely manner.

• Follow established payroll procedures to support compliance with multi-state wage and hour laws and applicable tax regulations.

Benefits Administration

• Administer day-to-day employee benefits programs, including health insurance, retirement plans, and leave management.

• Respond to employee benefits questions and coordinate with vendors to resolve enrollment, eligibility, and coverage issues.

• Support open enrollment activities, including employee communications, enrollment tracking, and documentation.

• Maintain accurate benefits records and process employee enrollments, changes, and qualifying life events.

• Assist with benefits reporting and identify recurring employee questions or administrative challenges.

People Analytics & HR Systems

• Maintain accurate employee records and ensure data integrity within the HRIS.

• Process employee changes, including new hires, terminations, transfers, and compensation updates.

• Generate routine HR reports and assist with data collection for workforce planning and operational needs.

• Support compliance reporting, audits, and recordkeeping requirements.

• Identify and correct data discrepancies to maintain accurate and reliable HR information.

Onboarding

• Coordinate new hire onboarding activities to ensure Day 1 readiness, including offer letters, documentation, checklists, and compliance requirements.

• Partner with internal teams to facilitate a smooth and positive onboarding experience.

• Track onboarding completion and follow up on outstanding tasks and documentation.

• Respond to new hire questions and provide guidance on HR policies, benefits, and onboarding processes.

• Gather onboarding feedback and identify opportunities to improve the new hire experience.

General HR Operations

• Support employee onboarding and offboarding processes, ensuring timely completion of required tasks and documentation.

• Serve as a point of contact for routine employee inquiries related to HR policies, procedures, and programs.

• Maintain accurate, organized, and compliant employee records.

• Coordinate offboarding activities, including documentation, system updates, and internal notifications.

• Assist with HR compliance activities, including employee documentation, reporting, and audits.

• Support the administration of HR programs and initiatives as assigned.

• Identify opportunities to streamline routine HR processes and improve the employee experience.

Qualifications:

• Bachelor’s degree in Human Resources, Business, or related field

• 2+ years of HR experience with strong ownership of onboarding

• Experience working in a startup or high-growth environment

• Proficiency with HRIS platforms (e.g., Rippling, ADP, Workday, or similar)

• Analytical skills (dashboards/BI tools a plus)

• High attention to detail and ability to manage sensitive information

• Solid understanding of employment laws and compliance requirements

Preferred Skills:

• Experience in aerospace, defense, manufacturing, or other regulated industries

• Familiarity with government compliance environments (e.g., audits, reporting standards)

• Experience building or scaling HR processes

• HR certification (PHR, SHRM-CP, or equivalent)

Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details.

Other Duties

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice.

Additional Eligibility Requirements

This position may require access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply.

Affirmative Action/EEO Statement

Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law.

Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact hr@castelion.com. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law.

Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation.

EAR/ITAR Requirements

This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate’s ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.