Ven Martin Gorick says it will be September 2016 at the earliest - nearly two years since the last bishop, Rt Revd John Pritchard, retired.
Dioceses usually have to wait less than a year for a new bishop to be appointed.
Rt Revd Colin Fletcher is acting Bishop of Oxford until a permanent appointment is made.
The Diocese of Oxford, which also covers Berkshire and Buckinghamshire, has been waiting because the Crown Nomination Commission chose not to appoint any of the candidates they interviewed from a shortlist in May.
Premier has been told it is strictly confidential how many people were in the initial long-list, how many were interviewed on the shortlist, and why the Commission chose not to appoint any of them.
The Commission, made up of the two archbishops, six elected permanent members and six elected local representatives from the diocese in question, will not have a chance to pick the Bishop of Oxford again until March 2016.
Archdeacon Gorick told the Oxford Mail newspaper: "When [the commission] met earlier in May, no appointment was made and we have been told that we will have to wait until March 2016, before Oxford will be considered again.
"It's unlikely that we will have a Bishop of Oxford in post now until at least September 2016, which will be two years since Bishop John retired.
"We miss that leadership and the friendship of a trusted senior colleague."
The Archbishop of Canterbury, Most Revd Welby, specifically wrote a letter to Christians in the Diocese of Oxford after the Commission chose not to appoint a permanent bishop.
It said: "You will be aware that the Crown Nominations Commission (CNC) met on the 11th and 12th May to consider the nomination of the next Bishop of Oxford and to meet with possible candidates.
"I am writing to advise that the Commission has been unable to discern the candidate whom God is calling at this stage to be the next Bishop of Oxford. Under the election rules under which we operate, in a secret ballot no candidate received the required number of votes for nomination."
