diff --git a/src/bench/prevector.cpp b/src/bench/prevector.cpp
index 9b83c42693fd3..adc3d18de000c 100644
--- a/src/bench/prevector.cpp
+++ b/src/bench/prevector.cpp
@@ -87,6 +87,7 @@ static void PrevectorFillVectorDirect(benchmark::Bench& bench)
 {
     bench.run([&] {
         std::vector<prevector<28, T>> vec;
+        vec.reserve(260);
         for (size_t i = 0; i < 260; ++i) {
             vec.emplace_back();
         }
@@ -99,6 +100,7 @@ static void PrevectorFillVectorIndirect(benchmark::Bench& bench)
 {
     bench.run([&] {
         std::vector<prevector<28, T>> vec;
+        vec.reserve(260);
         for (size_t i = 0; i < 260; ++i) {
             // force allocation
             vec.emplace_back(29, T{});
diff --git a/src/rpc/output_script.cpp b/src/rpc/output_script.cpp
index 49f3a812437d5..5de2847be997d 100644
--- a/src/rpc/output_script.cpp
+++ b/src/rpc/output_script.cpp
@@ -123,6 +123,7 @@ static RPCHelpMan createmultisig()
             // Get the public keys
             const UniValue& keys = request.params[1].get_array();
             std::vector<CPubKey> pubkeys;
+            pubkeys.reserve(keys.size());
             for (unsigned int i = 0; i < keys.size(); ++i) {
                 pubkeys.push_back(HexToPubKey(keys[i].get_str()));
             }
diff --git a/src/test/checkqueue_tests.cpp b/src/test/checkqueue_tests.cpp
index a9a1e4707067a..b7014db4a5b9e 100644
--- a/src/test/checkqueue_tests.cpp
+++ b/src/test/checkqueue_tests.cpp
@@ -360,6 +360,7 @@ BOOST_AUTO_TEST_CASE(test_CheckQueueControl_Locks)
     auto queue = std::make_unique<Standard_Queue>(QUEUE_BATCH_SIZE, SCRIPT_CHECK_THREADS);
     {
         std::vector<std::thread> tg;
+        tg.reserve(3);
         std::atomic<int> nThreads {0};
         std::atomic<int> fails {0};
         for (size_t i = 0; i < 3; ++i) {
diff --git a/src/test/cuckoocache_tests.cpp b/src/test/cuckoocache_tests.cpp
index bb4c8c70938f3..f08c4d44287b6 100644
--- a/src/test/cuckoocache_tests.cpp
+++ b/src/test/cuckoocache_tests.cpp
@@ -224,6 +224,7 @@ void test_cache_erase_parallel(size_t megabytes)
     /** Spin up 3 threads to run contains with erase.
      */
     std::vector<std::thread> threads;
+    threads.reserve(3);
     /** Erase the first quarter */
     for (uint32_t x = 0; x < 3; ++x)
         /** Each thread is emplaced with x copy-by-value
diff --git a/src/test/fuzz/txorphan.cpp b/src/test/fuzz/txorphan.cpp
index 5129c05a3977f..31af1afff52d3 100644
--- a/src/test/fuzz/txorphan.cpp
+++ b/src/test/fuzz/txorphan.cpp
@@ -38,6 +38,7 @@ FUZZ_TARGET(txorphan, .init = initialize_orphanage)
 
     TxOrphanage orphanage;
     std::vector<COutPoint> outpoints; // Duplicates are tolerated
+    outpoints.reserve(200'000);
 
     // initial outpoints used to construct transactions later
     for (uint8_t i = 0; i < 4; i++) {
@@ -55,12 +56,14 @@ FUZZ_TARGET(txorphan, .init = initialize_orphanage)
             const auto num_out = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(1, 256);
             // pick outpoints from outpoints as input. We allow input duplicates on purpose, given we are not
             // running any transaction validation logic before adding transactions to the orphanage
+            tx_mut.vin.reserve(num_in);
             for (uint32_t i = 0; i < num_in; i++) {
                 auto& prevout = PickValue(fuzzed_data_provider, outpoints);
                 // try making transactions unique by setting a random nSequence, but allow duplicate transactions if they happen
                 tx_mut.vin.emplace_back(prevout, CScript{}, fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(0, CTxIn::SEQUENCE_FINAL));
             }
             // output amount will not affect txorphanage
+            tx_mut.vout.reserve(num_out);
             for (uint32_t i = 0; i < num_out; i++) {
                 tx_mut.vout.emplace_back(CAmount{0}, CScript{});
             }
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index 8e2b8639c2895..38be59fb64b30 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -79,6 +79,7 @@ template<typename B = uint8_t>
 {
     const size_t n_elements = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, max_vector_size);
     std::vector<std::string> r;
+    r.reserve(n_elements);
     for (size_t i = 0; i < n_elements; ++i) {
         r.push_back(fuzzed_data_provider.ConsumeRandomLengthString(max_string_length));
     }
@@ -90,6 +91,7 @@ template <typename T>
 {
     const size_t n_elements = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, max_vector_size);
     std::vector<T> r;
+    r.reserve(n_elements);
     for (size_t i = 0; i < n_elements; ++i) {
         r.push_back(fuzzed_data_provider.ConsumeIntegral<T>());
     }
diff --git a/src/test/rpc_tests.cpp b/src/test/rpc_tests.cpp
index 5089f3e8e33fe..87303d7417498 100644
--- a/src/test/rpc_tests.cpp
+++ b/src/test/rpc_tests.cpp
@@ -428,6 +428,7 @@ BOOST_AUTO_TEST_CASE(rpc_getblockstats_calculate_percentiles_by_weight)
 {
     int64_t total_weight = 200;
     std::vector<std::pair<CAmount, int64_t>> feerates;
+    feerates.reserve(200);
     CAmount result[NUM_GETBLOCKSTATS_PERCENTILES] = { 0 };
 
     for (int64_t i = 0; i < 100; i++) {