Exhibit 31.1

Principal Officer's Certification

Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002

I, David H. Ferdman, Interim President and Chief Executive Officer, certify that:

1. I have reviewed this Form 10-K/A of CyrusOne Inc.; and

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.