Background and purpose Optimizing speech-language therapy (SLT) regimens for maximal aphasia recovery is a clinical-research priority. We examined associations between SLT intensity (hours/weekly), dosage (total hours), frequency (days/weekly), duration (weeks), delivery (face-to-face, computer-supported, individual-tailoring, home-practice), content, and language outcomes for people with aphasia. Methods Databases including MEDLINE and Embase were searched (inception-09/2015). Published, unpublished and emerging trials including SLT and ≥10 Individual Participants’ Data (IPD) on aphasia, language outcomes and time post-onset were selected. Patient-level data on stroke, language, SLT and trial risk of bias were independently extracted. Outcome measurement scores were standardized. A statistical inferencing, one-stage, random effects, network meta-analysis approach filtered IPD into an optimal model examining SLT regimen for overall-language, auditory comprehension, naming and functional-communication pre-post intervention gains, adjusting for a-priori defined covariates (age, sex, time post-stroke, baseline aphasia severity), reporting estimates of mean change scores (95% CI). Results Data from 959IPD (25 trials) were included. Greatest gains in overall-language and comprehension were associated with >20to 50 hours SLT dosage (18·37 [10.58, 26·16] Western Aphasia Battery-Aphasia-Quotient; 5.23 [1·51, 8·95] Aachen Aphasia Test-Token Test). Greatest clinical overall-language, functional-communication and comprehension gains were associated with 2-4 and 9+ SLT hours/weekly.Greatest clinical gains were associated with frequent SLT for overall-language, functional-communication (3-5+ days/weekly) and comprehension (4-5 days/weekly). Evidence of comprehension gains was absent for SLT ≤20 hours, <3 hours/weekly and ≤3 days/weekly. Mixed receptive-expressive therapy, functionally-tailored, with prescribed home-practice was associated with greatest overall gains. Relative variance was <30%. Risk of trial-bias was low-to-moderate;low for meta-biases. Conclusions Greatest language recovery was associated with frequent, functionally-tailored, receptive-expressive SLT, with prescribed home-practice at a greater intensity and duration than reports of usual clinical services internationally. These exploratory findings suggest critical therapeutic ranges, informing hypothesis-testing trials and tailoring of clinical services.