The Cardiff-headquartered company has 20 staff and its markets include banner stands, building wraps, fabric vehicles and signs.
Co-director Lee Saltmarsh said the certification was an important addition to the company: "It is a powerful statement about how seriously we consider our impact on the environment.
"Any changes we can make to reduce our impact, and the waste we produce, while increasing efficiency for clients is a welcome move."
ACT's clients include the British Army and the Welsh Assembly Government.
The ISO 14001 standard was audited and awarded by Bureau Veritas.