Inclusion Criteria:

* Patient must have hematologic malignancy that meets institutional eligibility requirements for cord blood transplant
* Malignancies included are:

* Acute leukemia, including acute myeloid leukemia (AML), biphenotypic acute leukemia or mixed-lineage leukemia, acute lymphoblastic leukemia (ALL); all patients must be in complete response (CR) as defined by \< 5% blasts by morphology/flow cytometry in a representative bone marrow sample with adequate cellularity to assess remission status
* Myelodysplasia (MDS) International Prognostic Scoring System (IPSS) intermediate (Int)-2 or high risk (i.e., RAEB, RAEBt) or refractory anemia with severe pancytopenia or high risk cytogenetics; blasts must be \< 10% in a representative bone marrow aspirate
* Chronic myeloid leukemia excluding refractory blast crisis; to be eligible in first chronic phase (CP1) patient must have failed or be intolerant to tyrosine kinase inhibitor therapy
* High dose TBI regimen: 18 to =\< 45 years
* Intermediate intensity regimen: 18 to =\< 65 years
* Patients 18 to =\< 45 years: Karnofsky (\>= 18 years old) \>= 70 or Eastern Cooperative Oncology Group (ECOG) 0-1
* Patients \> 45 to =\< 65 years: Karnofsky \>= 70 or ECOG 0-1 and non-age adjusted comorbidity index =\< 5
* Calculated creatinine clearance must be \> 60 mL and serum creatinine =\< 2 mg/dL
* Total serum bilirubin must be \< 3 mg/dL unless the elevation is thought to be due to Gilbert's disease or hemolysis
* Transaminases must be \< 3 x the upper limit of normal per reference values of treating institution
* Carbon monoxide diffusing capability (DLCO) corrected \>= 60% normal (may not be on supplemental oxygen)
* Left ventricular ejection fraction \>= 50% OR
* Shortening fraction \> 26%
* Ability to understand and the willingness to sign a written informed consent form
* DONOR: Minimum requirement: The cord blood (CB) unit must be matched at a minimum at 4/6 HLA-A, B antigens and DRB1 allele with the recipient; therefore, 0-2 mismatches at the A or B or DRB1 loci based on intermediate resolution at HLA-A, B and high resolution allele level typing at HLA- DRB1 are allowed
* DONOR: Institutional guidelines for HLA-match may be followed as long as the minimum criteria for HLA-matching as above are met
* DONOR: The CB unit selected for transplant must have a MINIMUM of 2.5 x 10\^7 TNC/kg
* DONOR: The minimum recommended CD34/kg cell dose is 1.7 x 10\^5 CD34/kg
* DONOR: A backup unit, must be identified and reserved prior to the start of the treatment plan for possible infusion in the unlikely event of poor post-thaw viability of the primary CB unit. A suitable back up unit will be considered, as follows:

* i. Must be matched at a minimum at 4/6 HLA-A, B, DRB1 loci with the recipient. Therefore 0-2 mismatches at the A or B or DRB1 loci based on intermediate resolution A, B antigen and DRB1 allele typing for determination of HLA-match is allowed (Fred Hutch Protocol 2010- Appendix V).
* ii. Must contain a MINIMUM of 1.5 x 10\^7 TNC/kg to ensure the same requirement we use for a standard double CBT per CB selection guideline (Fred Hutch Protocol 2010- Appendix V).

Exclusion Criteria:

* Uncontrolled viral or bacterial infection at the time of study enrollment
* Active or recent (prior 6 month) invasive fungal infection unless cleared by infectious disease (ID) consult
* History of human immunodeficiency virus (HIV) infection
* Pregnant or breastfeeding
* Prior allogeneic transplant
* Central nervous system (CNS) leukemic involvement not clearing with intrathecal chemotherapy; diagnostic lumbar puncture is to be performed