**Exhibit 31.2**

**CERTIFICATIONPURSUANT SECTION 302 OFTHE SARBANES-OXLEY ACT OF 2002**

I,Richard Tennant, Chief Financial Officer of iBasis, Inc., a Delawarecorporation, doing business in Burlington, Massachusetts, certify that:

1.                 Ihave reviewed this annual report of Form 10-K of iBasis, Inc.;

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

3.                 Basedon my knowledge, the financial statements, and other financial informationincluded in this annual report, fairly present in all material respects thefinancial condition, results of operations and cash flows of the registrant asof, and for, the periods presented in this annual report;

4.                 Theregistrant’s other certifying officers and I are responsible for establishingand maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e) and internal control over financial reporting (as definedin Exchange Act Rules 13a-15(f) and 15d-15(f)) for theregistrant and we have:

a)               Designedsuch disclosure controls and procedures, or caused such control procedures tobe designed under our supervision, to ensure that material information relatingto the registrant, including its consolidated subsidiaries, is made known to usby others within those entities, particularly during the period in which thisannual report is being prepared;

b)              Designedsuch internal control over financial reporting, or caused such internal controlover financial reporting to be designed under our supervision, to providereasonable assurance regarding the reliability of financial reporting and thepreparation of financial statements for external purposes in accordance withgenerally accepted accounting principles.

c)               Evaluatedthe effectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thereport based on such evaluation; and

d)              Disclosedin this report any change in the registrant’s internal control over financialreporting that occurred during the registrant’s most recent fiscal quarter (theregistrant’s fourth quarter in the case of an annual report) that hasmaterially affected, or is reasonably likely to materially affect, the registrantsinternal control over financial reporting; and

5.                 Theregistrant’s other certifying officer and I have disclosed, based on our mostrecent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of registrant’s board ofdirectors (or persons performing the equivalent functions):

a)               Allsignificant deficiencies and material weaknesses in the design or operation ofinternal control over financial reporting which are reasonably likely toadversely affect the registrant’s ability to record, process, summarize andreport financial information; and

b)              Anyfraud, whether or not material, that involves management or other employees whohave a significant role in the registrant’s internal control over financialreporting.
| Date: June 8, 2007 | /s/ Richard Tennant                                                     |
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|                    | Richard Tennant  Chief Financial Officer  (Principal Financial Officer) |

 

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